ARTICLES

Nephrotoxicity of Acyclovir and Ganciclovir in Rats: Evaluation of Glomerular Hemodynamics

MARIA DE FATIMA FERNANDES DOS SANTOS,* OSCAR FERNANDO PAVAO DOS SANTOS,* MIRIAN APARECIDA BOIM,* CLARA VERSOLATO RAZVICKAS,* LUIS ANTONIO RIBEIRO DE MOURA,t HORACIO AJZEN,* and NESTOR SCHOR* *Nephrology Division and tPathology Department, Escola Paulista de Medicina, S#{227}oPaulo, Brazil.

Abstract. Whole-kidney function and glomerular hemodynam- 2.40 X l0’ dyn . s cm5 in the chronic group, P < 0.05) and ics were evaluated after acute (50 mg/kg, iv, in bolus) and a severe reduction in glomerular plasma flow rate (QA) short-term chronic (50 mg mg/kg, ip, 5 days) acyclovir (ACV) (152.6 ± 29.5 to 103.8 ± 27.8 nL/min in the acute group and and short-term chronic ganciclovir (Gan; 30 mg/kg, ip, 5 days) 149.1 ± 29.8 to 68.5 ± 10.0 nL/min in the chronic group, P < treatment in euvolemic Munich-Wistar rats. The evaluation of 0.05). However, the glomerular ultrafiltration coefficient, Kf, whole-kidney function of the ACV groups showed a significant was changed only in the chronic group (0. 1002 ± 0.0165 to reduction in total GFR (0.96 ± 0. 10 to 0.28 ± 0.02 mL/min in 0.0499 ± 0.0090 nL/(s . mm Hg), P < 0.05). After Gan the acute group, P < 0.05, and 1 .04 ± 0.09 to 0.33 ± 0.04 treatment, no changes were observed in GFR ( 1.04 ± 0.09 to mL/min in the chronic group, P < 0.05) with a marked 0.96 ± 0.08 mL/min, with the maintenance of RPF (2.57 ± increase in total renal vascular resistance (TRVR) (33 ± 5 to 0.36 to 2.66 ± 0.34 mL/min) and a nonsignificant reduction in

122 ± 26 mm Hg . min/mL in the acute group and 28 ± 3 to TRVR (28 ± 3 to 20 ± 3 mm Hg . min/mL. The short-term

74 ± 1 8 mm Hg . min/mL in the chronic group, P < 0.05) and Gan treatment also showed a different pattern in glomerular a reduction in RPF (2.29 ± 0.25 to 0.81 ± 0.15 mL/min in the hemodynamics by inducing an elevation in SNGFR (38.7 ± acute group and 2.57 ± 0.36 to 1 .30 ± 0.40 mL/min in the 5.7 to 50.3 ± 2.8 nL/min, P < 0.05) with no changes in QA chronic group, P < 0.05). Conversely, urinary flow (V’) was (150 ± 30 to 135 ± 22 nL/min) and a mild vasodilation, RT unchanged (3.6 ± 0.4 to 3.6 ± 0.2 j.tUmin in the acute group) (3.7 ± 0.5 to 2.7 ± 0.3 X lO’#{176}dyn . . cm5, P < 0.05) or elevated (3.7 ± 0.6 to 6.6 ± 1 .4 pL/min in the chronic associated with an increment in Kf (0. 1002 ± 0.0165 to group, P < 0.05). The evaluation of glomerular hemodynamics 0.2400 ± 0.0700 nL/(s . mm Hg), P < 0.05). Thus, ACV after ACV treatment showed a reduction in single-nephron induced acute renal failure by reducing GFR and SNGFR by an GFR (SNGFR) (46.4 ± 5.3 to 26.2 ± 3.4 nL/min in the acute increase in TRVR and RT with a reduction in RPF and QA. group and 38.7 ± 5.7 to 21.1 ± 5.7 nL/min in the chronic Also, after short-term treatment with ACV, a reduction in Kf group, P < 0.05), a significant elevation in total arteriolar led to a reduction of SNGFR. On the other hand, Gan treatment resistance (RT) (2.90 ± 0.44 to 4.94 ± 0.77 X lOb did not induce acute renal failure by the adopted techniques. dyn . . cm’5 in the acute group and 3.72 ± 0.45 to 9.00 ± (J Am Soc Nephrol 8: 361-367, 1997)

Effective antiviral drug therapy is currently available, espe- In fact, herpes and cytomegalovirus infections are a major cially in the area of herpes infections. The use of acyclovir cause of morbidity and mortality in patients with AIDS (2). (ACV) has become an established part of clinical practice, and Also, cytomegalovirus is well recognized as the most impor- other compounds such as ganciclovir (Gan) an ACV-like drug, tant pathogen in recipients of bone marrow (5) and renal are being increasingly used in the treatment of herpes simplex transplants (6), and it is known to be responsible for more than and cytomegalovirus diseases in immunocompromised hosts. 90% of viral infection recurrence in AIDS patients (7,8). Thus, because vaccines for these pathogens are still being On this basis, the potential side-effects of these compounds developed, antiviral agents will continue to play a major role in are a source of concern in medical practice, and many studies the management of all virus infections (1-4). about ACV and some about Gan toxicity have been conducted by several investigators. Effects such as neurotoxicity and nephrotoxicity have already been reported after ACV treat- Received April 1 1, 1995, Accepted July 8, 1996. ment, but renal damage is the most common and speculative Correspondence to Dr. Nestor Schor, Nephrology Division, Escola Paulista de side-effect of this antiviral drug (9). Gan seems to be respon- Medicina, Rua Botucatu. 740, 04023-062 S#{227}oPaulo, 5. P. Brasil. sible for neutropenia in 30% of patients, but no evidence of 1046-6673/0803-0361$03.00/0 Journal of the American Society of Nephrology renal damage has been associated with this compound (9). The Copyright © 1997 by the American Society of Nephrology possibility that Gan is not nephrotoxic, and its potential use in 362 Journal of the American Society of Nephrology the management of other viral infections, encourages its use as ip. The fourth group received chronic Gan treatment, 30 mg/kg body an alternative to ACV in cases of renal failure, and stimulated wt, ip, daily for 5 days. All rats were allowed free access to water and this study on a comparison of their effects on renal function. a standard rat-pellet diet until the morning of the study. Rats were In fact, the presumed mechanism of ACV-induced renal anesthetized with Inactin (BYK, Konstanz, Germany), 100 mg/kg, ip, placed on a temperature-regulated table, and monitored with an elec- damage was first demonstrated by animal studies. Rats that tronic rectal thermometer (Simpson Co., Chicago, IL) to keep body received intravenous ACV (20 mg/kg per d) developed an temperature between 37 and 37.5#{176}C.After the rats underwent trache- obstructive nephropathy secondary to drug crystal formation in otomy, the left femoral artery was catheterized with PE-50 polyeth- collecting ducts (10,1 1). Cristalluria was also observed to be ylene tubing, and approximately 60 pL of arterial blood was collected dose-dependent and reversible, depending on the drug discon- for baseline hematocnt (Hct) and protein (CA0) determination. The tinuation. Studies performed in mice receiving single 50-mg ip same arterial catheter was also used for subsequent periodic blood doses of ACV demonstrated crystal formation in collecting sampling and evaluation of mean femoral arterial pressure (MAP) tubules, with gradual diminution in refractile material over with an electronic transducer (Model P23Db; Statham Instruments time (12). After only 20 mm of the infusion, crystals were Div., Gould Inc., Hato Rey, Puerto Rico) connected to a direct-writing observed in the renal pelvis. On the other hand, the histologic recorder (Model 2.200; Gould Inc., Cleveland, Ohio). Polyethylene catheters were also introduced into the right and left jugular veins for changes in the affected kidneys were described as minimal, infusion of inulin, paraaminohippunc acid (PAH), and isoncotic rat with increased basophils, desquamation of collecting tubule serum. The animals were then infused intravenously with 10% inulin epithelial cells, and mild interstitial edema. Nevertheless, fine- and a 2% PAH solution in 0.9% sodium chloride at a rate of 1.2 mL/h. needle crystals consistent with ACV crystals have been de- Isoncotic rat serum was infused into the left vein to replace surgical tected by microscopy and paper chromatograph in urine spec- losses and thus maintain the animals in euvolemic conditions (14). imens from affected humans. A kidney autopsy specimen of Laparotomy was then performed, and a PE-lO polyethylene catheter one patient showed moderate congestion, normal glomeruli was introduced into the left ureter for collection of timed urine and tubules, and no evidences of crystals (1 3). Also, acute samples, after which rats were routinely prepared for micropuncture tubular necrosis and absence of crystalluria and crystal depo- studies (17-19). sition within the kidney specimen were demonstrated on a biopsy of a patient affected by ACV nephropathy (14). More- Micropuncture Studies over, crystal dissolution after the fixation methods used and the Glomerular hemodynamic evaluations were done by micropuncture time between the experiment and the morphological studies technique. Exactly timed (1 to 3 mm) samples of tubular fluid were must be taken into consideration, because they may eliminate collected from surface convolutions of at least three nephrons for the obstruction mechanism of ACV nephropathy. However, no determination of flow rate and inulin concentration, and calculation of glomerular effect has been demonstrated on the level of renal single-nephron GFR (SNGFR). Simultaneously, two or three samples microcirculation when ACV is given in a dose (acute or of femoral arterial blood were obtained during each period for deter- mination of systemic arterial pressure, Hct, total protein, inulin, and chronic) that does not cause crystalluria, crystal deposition, or PAH concentration in plasma. tubular obstruction. To estimate the colloidal osmotic pressure of plasma entering and Other animal studies about different nephrotoxic agents have leaving glomerular capillaries, we measured protein concentrations in also demonstrated severe glomerular hemodynamic alterations efferent arteriole (CE) blood plasma, as previously described (21). CA without important renal morphology changes (e.g., gentamicin, (in the femoral artery) was taken as a parameter of protein concen- cisplatin), suggesting that the development of acute renal fail- tration in the afferent arteriole. At the same time, hydraulic pressures ure (ARF) in these experimental models may be of functional were measured in the superficial structures of the kidneys by a origin (15,16). continuous recording system (1PM Inc., San Diego, CA). Micropi- Thus, to investigate the physiology of the renal impairment pettes with outer tip diameters of 2 to 4 m and containing 2.0 M induced by ACV in the absence of crystalluria, and the possible sodium chloride were used. Hydraulic pressure output from the servo- renal events after Gan treatment, groups of rats submitted to system was channeled via an electronic transducer (Statham model acute or chronic short-term treatment with ACV or to chronic P23Db) to a second channel of the recorder. Direct measurements of hydraulic pressure in single glomerular capillaries (P), proximal short-term treatment with Gan were evaluated. Also, a group of tubules (UT)’ efferent arterioles (PEA)’ and third-order peritubular rats receiving only vehicle was used as a control. Whole renal capillaries (Pr) were recorded in each rat. function and glomerular hemodynamics were evaluated in all At the end of the functional studies, kidney samples were fixed in animals. In addition, pathologic analysis of kidney specimens a solution containing 2% glutaraldehyde, Bouin, Methanol, or Du- was carried out in the ACV group. bosch.

Materials and Methods Analytical Procedures Studies were performed in four groups of adult male Munich- The concentration of inulin in tubular fluid was determined, usually

Wistar rats weighing 250 to 300 g. The first group (N = 1 1, acute in duplicate, by the microfluorescence method of Vurek and Pegram ACV) after a period of equilibration received an intravenous injection (22). Inulin and PAH concentrations in plasma and urine were ob- of ACV, 50 mg/kg body wt in bolus (3 mm infusion) in a O.l-mL tamed by the macroanthrone method of Fuhr et a!. (23) and by the volume. The second group (N 10, chronic ACV) was treated with method of Smith et a!. (24), respectively. Protein concentration in the

ACV 50 mg/kg body wt, ip, daily for 5 days. The third group (N = 9) femoral artery was determined by refractometry and corrected accord- was also treated daily for 5 days with ACV-vehicle (saline), 0.1 mL ing to a curve constructed by the method of Lowry and modified by Acyclovir and Ganciclovir Nephrotoxicity in Rats 363

Schachterle (25). The protein concentration in efferent arteriole and mm Hg). No change in Kf (0. 1 149 ± 0.0200 to 0. 1 33 1 ± femoral arterial blood plasma was determined using a microfluorcolo- 0.0222 nL/(s . mm Hg)) was observed, compared with the rimeter by the method of Viets et a!. (25). period before drug infusion, even when only animals in dis- Glomerular filtration rate was evaluated by inulin clearance, and equilibrium of filtration were used. RPF by PAH clearance. Total renal vascular resistance (TRVR) was Short-term ACV administration also induced nonoliguric estimated as the MAPIRPF ratio. The filtration fraction (FF) was ARF, considering that urine flow rate increased (3.7 ± 0.6 to calculated as the quotient of GFR and RPF. Values of GFR and RPF were corrected for kidney weight. 6.6 ± 1.4 Umin, P < 0.05). Significant decreases in GFR Colloidal osmotic pressures, hydraulic pressures, and SNGFR al- (1.04 ± 0.09 to 0.33 ± 0.04 mL/min, P < 0.05) and RPF low the calculation of single-nephron filtration fraction (SNFF), initial (2.57 ± 0.36 to 1.30 ± 0.40 mL/min, P < 0.05) were ob- glomerular capillary plasma flow rate (QA). afferent (RA), efferent served. The latter was the result of an increase in TRVR (28 ± (RE), and total (RT RA + RE) arteriolar resistances, and glomerular 3 to 74 ± 18 mm Hg . min/mL, P < 0.05). Thus, FF was also ultrafiltration coefficient (Kf), using equations given elsewhere (25). maintained (43 ± 6 to 40 ± 1%) in this group (Table 6). The evaluation of glomerular hemodynamics after short- Statistical Analysis term chronic ACV administration showed that ACV caused a Data were analyzed statistically by the paired and unpaired t test, marked decrease in SNGFR (38.7 ± 5.7 to 21 . 1 ± 5.7 nL/min, with the level of statistical significance set at P < 0.05. All data are P < 0.05) (Table 7). This reduction was accompanied by a reported as mean ± SE. decline in QA (149.1 ± 29.8 to 68.5 ± 10.1 nL/min, P < 0.05) Results as a result of an important increase in RA (2.34 ± 0.36 to 4.10 ± 0.80 x 1O’#{176}dyn . . cm5, P < 0.05), RE (1.18 ± Tables 1 and 2 summarize the results of general data and 0.16 to 4.90 ± 0.90 x lO’#{176}dyns cm5, P < 0.05), and RT whole-kidney function for the acute and chronic ACV groups. (3.72 ± 0.45 to 9.00 ± 2.40 X lOb dyn . . cm5, P < 0.05). Initial body weight (BW1), kidney weight (KW), MAP, initial Because P- (45 ± 2 to 55 ± 4 mm Hg, P < 0.05) and T and final hematocnt (Hct and Hct1), and initial and final (14 ± 1 to 24 ± 2 mm Hg, P < 0.05) increased proportion- afferent protein concentration (CAO and CA) did not differ ately, LW remained unchanged (31 ± 1 to 31 ± 2 mm Hg). In between groups. contrast to the acute group, mean Kf was markedly reduced in Nonoliguric ARF was detected on the basis of urine output ± after acute intravenous infusion of ACV (3.6 ± 0.4 to 3.6 ± this group (0.1002 0.0165 to 0.0499 ± 0.0090 nL/(s mm < 0.2 L/min). Moreover, GFR was hardly decreased (0.96 ± Hg), P 0.05) (Table 8), even in a condition of disequilibrium 0.10 to 0.28 ± 0.02 mL/min, P < 0.05) because of severe of filtration. Gan treatment caused a different renal function pattern. increase in TRVR (33 ± 5 to 122 ± 26 mm Hg . min/mL, P < 0.05), which also determined a decline in RPF (2.29 ± 0.25 to Overall renal function was unchanged in this group, compared 0.81 ± 0.15 mL/min, P < 0.05). This proportional decrease in with the saline control group. V’ was also maintained (3.7 ± GFR and RPF maintained FF at levels that were unchanged 0.6 to 3.2 ± 0.6 pL/min) and GER unchanged (1.04 ± 0.09 to (43 ± 1 to 38 ± 1%) (Table 3). 0.96 ± 0.08 mL/min). Despite a reduction in RVRT (28 ± 3 to

Tables 4 and 5 summarize the results of superficial nephron 20 ± 3 mm Hg . min/mL, P < 0.05), RPF was unchanged function for the acute group. A significant decrease in SNGFR (2.57 ± 0.36 to 2.66 ± 0.34 mL/min). The maintenance of (46.4 ± 5.3 to 26.2 ± 3.4 nL/min, P < 0.05) was observed. TRVR and RPF left FF unchanged (43 ± 6 to 38 ± 3%). The Increases in RA (1.90 ± 0.32 to 3.66 ± 0.63 X lO’#{176} hemodynamic pattern for this group was similar to the overall ± ± dyn . . cm5, P < 0.05), RE (l.O ± 0.15 to 1.29 ± 0.20 X function, with a mild increase in SNGFR (38.7 5.7 to 50.3

1010 dyn . . cm5, P < 0.05), and RT (2.90 ± 0.44 to 4.94 ± 2.8 nL/min). This effect was caused by an elevation in Kf

0.77 x iO’#{176}dyn . . cm5, P < 0.05) were also observed in (0.1002 ± 0.0165 to 0.2400 ± 0.070 nL/(s . mm Hg, P < this group, leading to an important reduction on QA (152.6 ± 0.05) that was associated with maintenance of QA (149. 1 ± 29.5 to 103.8 ± 27.8 nL/min, P < 0.05). Because GC (44 ± 29.8 to 134.9 ± 9.8 nUmin) and a decline in RT (3.7 ± 0.5 to

2to42 ± 2mmHg)andP(l6 ± 1 to 18 ± 1 mmHg) 2.7 ± 0.3 x 10’#{176}dyn . s cm5, P < 0.05) (Figure 1). The remained unchanged, P was not affected (28 ± 2 to 24 ± 1 predominant reduction in RE (1. 18 ± 0. 16 to 0.61 ± 0.09 X

Table 1. Summary of general data for the acute acyclovir (ACV) group

BW KW Hct’ Hct ‘ b CA MAP ‘-AO Group (mm Hg) (g) (%) (g/dL)

Pre-acute ACV 261 ± 7 1.4 ± 0.1 130 ± 4 45 ± 1 46 ± 1 5.1 ± 0.1 5.0 ± 0.4 Post-acute ACV 46 ± 1 5.0 ± 0.2

a Values shown are means ± SE. BW, body weight; KW, kidney weight; MAP, mean arterial pressure; Hct, hematocrit, CA, afferent protein. b The subscript 0 refers to baseline values at the beginning of anesthesia. 364 Journal of the American Society of Nephrology

Table 2. Summary of general data for the chronic ACV group#{176}’

BWh (g) MAP Hct() Hct CAO CA Treatment KW (g) (mm H in fn g (%) (g/dL)

Vehicle 250 ± 6 258 ± 7 1.0 ± 0.4 138 ± 5 45 ± I 44 ± 1 5.1 ± 0.1 5.1 ± 0.1 Chronic 265±6 230c±8 1.1±0.1 132±6 46±1 44±1 5.2±0.1 5.3±0.1

a Values shown are means ± SE. Abbreviations are defined in the footnote to Table 1. b initial body wt; fn, final body wt.

C p < o.os, final versus initial body weight.

Table 3. Summary of whole-kidney function data for the acute ACV groupa

V’ GFR RPF TRVR Group (L/min) (mL/min) FF (%) (mm Hg . min/mL)

Pre-acute ACV 3.6 ± 0.4 0.96 ± 0.10 2.29 ± 0.25 43 ± I 33 ± 5 Post-acute ACV 3.6 ± 0.2 0.28 ± 002b 0.81 ± o15b 38 ± 1 122 ± 26b

a Values shown are means ± SE. V’. urinary flow; FF, filtration fraction; TRVR, total renal vascular resistance. 1 p < 0.05, pre-acute ACV versus post-acute ACV.

Table 4. Glomerular hemodynamic measurements for the acute ACV groupu

SNGFR QA GC Group SNFF (%) zP (nL/min) (mm Hg)

Pre-acute ACV 46.4 ± 5.3 152.6 ± 29.5 34 ± I 44 ± 2 16 ± 1 28 ± 2 28 ± 1 Post-acute ACV 26.2 ± 103.8 ± 278b 31 ± 1 42 ± 2 18 ± 1 24 ± 1 22 ± 1

a Values shown are means ± SE. SNGFR, single-nephron GFR; QA’ glomerular plasma flow rate; SNFF, single-nephron filtration fraction; GC’ single glomerular capillary pressure; T’ proximal tubule pressure; uP, transcapillary hydraulic pressure gradient; PEA’ efferent arteriolar pressure. h p < o.oos, post-acute ACV versus pre-acute ACV.

Table 5. Glomerular hemodynamic data of acute ACV group#{176}

RA R1: RT CA CF Group Kf Eq/Des (nL/(s . mm Hg)) (X lOtO dyn . s cm5) (g/dl)

Pre-acute ACV 1.90 ± 0.32 1.00 ± 0.15 2.90 ± 0.44 5.0 ± 0.1 7.7 ± 0.2 0.1 149 ± 0.0200 6/3 Post-acute ACV 3.66 ± 0.63” 1.29 ± 0.20” 4.94 ± 0.7D 5.0 ± 0.2 7 .4 ± 0.2 0.1331 ± 0.0222 6/3

a Values are shown as means ± SE. Eq/Des, equilibrium/disequilibrium ratio. All other abbreviations defined in preceding tables’ footnotes. b p < 0.05, pre-acute ACV versus post-acute ACV.

lOb dyn . s cm5, P < 0.05) when compared with the re- general population (2). Also, the incidence of cytomegalovirus duction in RA (2.34 ± 0.36 to 2.12 ± 0.24 X iO#{176} (CMV) infections in this population is high, and CMV is a dyn . s cm5) induced a nonsignificant decrease in P (31 ± major cause of morbidity and mortality in AIDS patients and in 2 to 24 ± 2 mm Hg). SNFF was also unchanged (3 1 ± I to recipients of bone marrow or solid organ transplants (1). In 38 ± 1%) (Figure 1). fact, the effective specific antiviral chemotherapy for HSV and CMV is still represented by ACV and Gan (3). Discussion Thus, the main purpose of this study was to determine the Precise data on the prevalence of herpes simplex virus possible damage of renal function induced by these two drugs (HSV) infections in immunocompromised individuals such as by submitting Munich-Wistar rats to ACV (acute and chronic AIDS patients and allograft recipients are not available, but treatment) and ganciclovir (chronic treatment), and evaluating evidence suggests that the rate parallels or exceeds that of the the overall renal function and glomerular hemodynamics of Acyclovir and Ganciclovir Nephrotoxicity in Rats 365

Table 6. Summary of whole-kidney function data for the chronic ACV group’

GFR RPF TRVR Treatment V (pt/mm) FF (%) (mm Hg . min/mL) (mL/min)

Vehicle 3.7 ± 0.6 1 .04 ± 0.09 2.57 ± 0.36 43 ± 6 28 ± 3 0.04 Chronic ACV 66b 1 .4 033b 1 30b 0.40 40 ± 1 74’ ± 18

a Values shown are means ± SE. V. volume; TRVR. total renal vascular resistance. All other abbreviations defined in preceding tables’ footnotes. b p < o.os, chronic ACV versus vehicle.

Table 7. Glomerular hemodynamic data for vehicle and chronic ACV groups#{176}#{176}

SNGFR QA SNFF GC- P’I’ tA Group (C/) (nL/min) C (mm Hg)

Vehicle 38.7 ± 5.7 149.1 ± 29.8 31 ± I 45 ± 2 14 ± I 31 ± I 21 ± 2

Chronic ACV 21.1 ± 57b 68.5 ± 101b 31 ± 1 55 ± 3h 24 ± 4h 31 ± 2 23 ± 2

Values shown are means ± SE. All abbreviations are defined in preceding tables’ footnotes. b p < 0.05, chronic ACV versus vehicle.

Table 8. Glomerular hemodynamic data for the chronic ACV group#{176}

RA RF R1 CA CF K Group Eq/Des LI H (X l0’#{176}dyn . 5 cm5) (g/dL) n s‘ mm g

Vehicle 2.34 ± 0.36 1.18 ± 0.16 3.72 ± 0.45 5.1 ± 0.1 7.7 ± 0.3 0.1002 ± 0.0165 7/3 Chronic ACV 4.10 ± 080b 4.90 ± 090h 9.00 ± 240h 0. 1b 0.3 0.0499 ± 0.0090” 6/4

a Values shown are means ± SE. All abbreviations are defined in preceding tables’ footnotes.

b p < 0.05, chronic ACV versus vehicle.

these animals by clearance and micropuncture techniques. A The glomerular hemodynamic studies of acute and chronic pilot study was performed (data not shown) to determine an ACV groups presented in this article demonstrated a reduction ACV dose that did not cause crystalluria or tubular obstruction. in SNGFR. The reduced SNGFR observed in acute ACV- In fact, only ACV has been associated with episodes of ARF in treated animals occurred as a result of a decline in QA. On the patients submitted to large dosages and long-term treatment other hand, the decline in SNGFR after short-term chronic (26), but the widespread clinical use of Gan led us to study the ACV treatment was not only the result of a reduction in QA. but side-effects of this drug also. also of an important decrease in Kf. These effects on QA ACV promoted ARF, with a reduction in GFR, marked reduction in both kinds of treatment with ACV may have been vasoconstriction, and maintenance or elevation of urine output. caused by severe vasoconstriction, as demonstrated by the Previous clinical observations showed increased urinary j32- elevations in RA and RE. These increments were probably microglobulin excretion in a patient submitted to ACV treat- mediated by hormonal actions. However, because flO hormonal ment, with no changes in serum creatinine. Therefore, because blockade was used in this study, we cannot conclude which this protein is filtered and reabsorbed by the proximal tubule, hormonal system is really involved in this ARF. this finding can indicate a probable ACV toxicity to this However, the apparent reduced P observed in this study, segment of the nephron (27). In fact, microperfusion studies when compared with the usual mean in the literature, cannot be with rats treated with ACV showed that the diffusional water responsible for the decrement in SNGFR because it is in permeability in the inner medullary collecting duct did not accordance with our laboratory pattern for this parameter under increase significantly when vasopressin was added to the bath, control conditions, as already demonstrated by Barros et al. as observed in the tubules of normal rats (28). In the study (303 I ), Santos et al. ( 1 7), and Haddad ci al. (32). presented here, the high urine output and the significant in- Kidney samples from animals of the ACV groups were crease in T are in accordance with the these observations, and analyzed for morphology by light microscopy techniques, and together suggest that a tubular defect in the handling of anti- no alteration was observed in glomerular or tubular morphol- diuretic hormone is really involved in this ARF. ogy by this method, even after four different methods of 366 Journal of the American Society of Nephrology

GFR SNGFR TRVR R RPF QA % From control

Figure 1. Percentage changes in overall function and glomerular hemodynamics in rats submitted to acute and chronic acyclovir and ganciclovir treatment. SNGFR, single-nephron GFR; TRVR, total renal vascular resistance; TT, total artenolar resistance; QA’ glomerular plasma flow rate; uP, transcapillary hydraulic pressure gradient; Kf, glomerular ultrafiltration coefficient. * P < 0.05, acute versus pre-acute; p < 0.05, ancyclovir versus saline; ** P < 0.05, ganciclovir versus saline. Filled bars, acute ACV; hatched bars, chronic ACV; dotted bars, chronic Gan.

fixation were used to reduce the possibility of dissolving lii- time administration of ACV. On the other hand, the glomerular bular drug crystals. hemodynamic alterations caused by acute and chronic toxicity In fact, the euvolemic condition of the rats submitted to this of ACV administration were found to be different. Thus, the study, with the dose adopted, could have protected them from role of vasoactive systems is probably modified during the accumulating crystals in renal tubules, and no obstructive event evolution of these two models of ACV nephrotoxicity. The was observed. Nevertheless, in our preliminary results (which repetitive administration of ACV could cause a modification of are not presented here because they were determined from a glomerular response to this drug, leading to a more important solely dosage-managing study), much larger doses of ACV (up mesangial cell contraction and consequent reduction on Kf. A to 300 mg/kg) induced ureter obstruction, and ACV crystals similar glomerular hemodynamic pattern for different periods were observed in this segment after an anuric period, which of administration has been also described for cyclosporine A can emphasize a dose-dependent mechanism for this signal. nephrotoxicity (29,30). Thus, this study’s model, with 50 mg/kg of ACV and the In contrast, Gan treatment did not affect overall renal func- glomerular changes observed, could also precede the obstruc- tion or glomerular hemodynamics, indicating that this drug-at tion observed when larger doses are administered. least in this model-had no side-effect on renal function, or As has been observed for some other nephrotoxic agents that the dosage used did not cause any renal alterations, despite (e.g., cisplatin, gentamicin, and cyclosporin A), a high dose of being higher than that used for humans. On the other hand, the these drugs is necessary to induce ARF (16,17,30,31). Also, increase in Kf observed in this group was responsible for a one should consider that the doses of ACV and Gan in this nonsignificant elevation on SNGFR, but the specific determi- study were very large in comparison with those used in hu- nants involved in this alteration cannot be explained once this mans-in fact, it is almost three times larger. However, it is parameter has been calculated only from a differential equation fundamental to reiterate that different patterns of drug resis- that involves the changes in the velocity protein concentration tance among species have been already extensively discussed in the whole glomerular capillary idealized by Deen et al. (26) (33,34), and in comparison with humans, the rat is much more and not measured. Exclusively, the real measurement of Kf resistant to nephrotoxic insults because of a larger proportion could specify which determinant, whether the hydraulic con- of kidney weight to body weight, and the relation of GFRJ ductivity or the available filtration area, has induced such a kidney weight is approximately three times that described for change in this coefficient. humans. This fact obligated our laboratory to choose the large In summary, this study has shown that ACV, at the dose dosage of each drug. used, induced a nonoliguric ARF and, in contrast to most Moreover, the lack of correlation between functional and studies about this drug, no tubular obstruction was detected in morphological injuries can also indicate that different patho- the animal’s kidneys by light microscopy. It is the first dem- genic mechanisms are involved in acute and chronic ACV onstration of ACV effects on renal microcirculation in the nephrotoxicity, as well as provide an explanation for the sud- absence of crystalluria. den decline of renal function sometimes observed after a first- Thus, although the evaluation of which hormones are in- Acyclovir and Ganciclovir Nephrotoxicity in Rats 367 volved in the renal disturbances observed after ACV adminis- 16. Schor N, Ichikawa I, Renke HG, Troy IL, Brenner BM: Patho- tration was not the objective of this article, the sole glomerular physiology of altered glomerular function in aminoglycoside- hemodynamic evaluation can itself demonstrate the severe treated rats. Kidney Int 19: 288-296, 1981 changes in the renal microcirculation that occur when the acute 17. Santos OFP, Boim MA, Barros RIG, Schor N: Role of platelet renal failure by ACV is installed. Indeed, the hormonal inves- activating factor in gentamicin and cisplatin nephrotoxicity. Kid- ney Int 4: 742-747, 1991 tigation, as well as cellular protocols, should really contribute 18. Maddox DA, Price DC, Rector FC Jr: Effects of surgery on to a better understanding of this nephrotoxicity. ACV, but not plasma volume and salt and water excretion in rats. Am J Physio! Gan, may cause renal damage, as shown by the overall renal 233: F600-F606, 1977 function and glomerular hemodynamic data in these studies. If 19. Ichikawa I, Maddox DA, Cogan MC, Brenner BM: Dynamics of the substitution of ACV by Gan could be considered in some glomerular ultrafiltration in euvolemic Munich-Wistar rats. Re- cases, this correlation between their different actions on renal na! Physio! 1: 121-131, 1978 function can lead to a more rational choice of antiviral drug to 20. 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