Influence of Acute Renal Failure on the Mononuclear Phagocytic System

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Brazilian Journal of Medical and Biological Research (2001) 34: 1169-1174 Influence of renal failure on phagocytic function 1169 ISSN 0100-879X

Influence of acute renal failure on the mononuclear phagocytic system

V.R.A. Sousa1, A.A. Sousa1, Departamentos de 1Cirurgia, 2Propedêutica, and 3Patologia, A. Petroianu1, C.J.R. Simal2 Faculdade de Medicina, Universidade Federal de Minas Gerais, and A.J.A. Barbosa3 Belo Horizonte, MG, Brasil

Abstract

Correspondence Several studies show the ability of macrophages to remove particles Key words A. Petroianu injected into the bloodstream. This function seems to be increased in · Renal failure Av. Afonso Pena, 1626, Apto. 1901 the presence of acute renal failure. The objective of the present study · Reticuloendothelial system 30130-005 Belo Horizonte, MG was to assess the phagocytic function of the main organs (spleen, liver · Phagocytosis Brasil and lung) of the mononuclear phagocytic system in renal and postrenal · Macrophage Fax: +55-31-274-7744 · failures. Fifteen rats (250-350 g) were divided into three groups (N = Scintigraphy Research supported by CNPq, 5): group I - control; group II - ligature of both ureters, and group III - FAPEMIG and PRPq-UFMG. bilateral nephrectomy. On the third postoperative day, all animals received an iv injection of 1 ml/kg 99mTc sulfur colloid. Blood samples were collected for the assessment of plasma urea, creatinine, sodium, and potassium concentrations and arterial gasometry. Samples of Received October 18, 1999 liver, spleen, lung and blood clots were obtained and radioactivity was Accepted June 5, 2001 measured. Samples of liver, spleen, lung and kidney were prepared for routine histopathological analysis. Plasma urea, creatinine and potassium concentrations in groups II and III were higher than in group I (P<0.05). Plasma sodium concentrations in groups II and III were lower than in group I (P<0.05). Compensated metabolic acidosis was observed in the presence of postrenal failure. Group II animals showed a lower level of radioactivity in the spleen (0.98) and lung (2.63), and a higher level in the liver (105.51) than control. Group III animals showed a lower level of radioactivity in the spleen (11.94) and a higher level in the liver (61.80), lung (11.30) and blood clot (5.13) than control. In groups II and III liver steatosis and bronchopneumonia were observed. Renal and postrenal failures seem to interfere with blood clearance by the mononuclear phagocytic system.

Introduction microorganisms, vital dyes and colloid particles. Most studies on spleen clearance have Infectious complications are still a major been based on the ability of macrophages to cause of morbidity and mortality in patients remove and retain particles injected into the undergoing regular dialysis treatment. This bloodstream. The capture of radioactively increased morbidity and mortality in the pres- labeled particles by macrophages may be ence of uremia seems to be due to dysfunc- verified in scintigraphic images. Otherwise, tion of polymorphonuclear leukocytes (1-4). quantitative assessment of spleen macrophage It has been established that the spleen can phagocytosis can be made using carbon col- retain obsolescent red blood cells, harmful loids (5-9).

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We have compared qualitative and quan- out the present investigation in order to de- titative methods for measuring spleen mac- termine the influence of renal and postrenal rophage function by studying scintigraphic failures on the phagocytic function of the images corresponding to histological sec- main organs (spleen, liver and lung) of this tions in different species which had received system. injections of radioactively labeled sulfur colloid and China ink (7). Material and Methods Our results have shown that sulfur colloid without technetium or with 99Tc or 99mTc, at A pilot study was undertaken to assess doses as small as those employed in routine survival time after surgical procedures using scintigraphy, is able to reduce significantly the 10 rats divided into two groups (N = 5): splenic capture of tiny carbon particles (China group I, bilateral nephrectomy, and group ink). The data suggest that the impairment of II, ligature of both ureters. Survival time splenic macrophage phagocytosis was caused was 48 h for group I and 60 h for group II. only by the sulfur colloid (7). The animals were highly uremic in both Based on the literature and on our previ- cases. ous investigation, we conclude that the ex- The study was carried out on 15 adult haustion of phagocytic cells and/or opsonins, Wistar rats of both sexes weighing 250 to or competition for blood components, may 350 g, obtained from the Medical School of play a pivotal role in phagocytic impairment. the Federal University of Minas Gerais. They Endocytosis of the sulfur colloid may be were maintained in cages with up to five responsible for macrophage saturation. An- animals of the same sex, with free access to other possibility is an inhibitory effect at the natural food and water. The animals were level of the macrophage membrane. A toxic divided into three groups (N = 5): group I - effect of the colloid on macrophage func- control (healthy animals - no procedures), tions has not been reported in the literature, group II - ligature of both ureters, and group and we did not find any alteration that might III - bilateral nephrectomy. suggest this hypothesis (7). The ligature of both ureters and nephrec- The blood clearance of abnormal or for- tomy were performed according to the fol- eign particles by phagocytic cells may be lowing steps. Inhalatory ether anesthesia was inhibited by previous administration of par- offered before the beginning of the opera- ticles such as several colloids and heparin to tion and when the rats started voluntary move- the blood. Despite uncertainty concerning ments during the 30-min experiment time; the mechanism of inhibition of blood clear- no respiratory depression was observed. The ance by prior administration of foreign par- abdominal cavity was entered through a mid- ticles, the process seems to operate at least line incision. partially through the blockade of the phagocytic mononuclear system by interfering with Group II macrophage function (8,10). We believe it is worth to propose that the Through a median laparotomy the retro- changes in internal environment provoked peritoneal space was opened and both ure- by uremia are able to modify the activity of ters were separated from surrounding tissue. different cells, including macrophages. If Each ureter was cut in the middle of four this is true, this phenomenon could influ- ligatures (using 5-0 polyglycolic acid thread). ence the phagocytic function of this system. The abdominal cavity of all rats was closed Following a line of research related to the in two layers with 2-0 polyglycolic acid mononuclear phagocytic system, we carried thread.

Braz J Med Biol Res 34(9) 2001 Influence of renal failure on phagocytic function 1171

Group III ether anesthesia, and the rats did not present any sign of respiratory failure during the 2- The pedicles of both kidneys were dis- min operative time. sected close to these organs in the retroperi- Samples of liver, spleen, lung and kidney toneum. The posterior parietal peritoneum were removed from all rats, prepared for and the tissue surrounding the kidneys were routine histopathological analysis, and removed. The Gerota’s fasciae of the kid- stained with hematoxylin and eosin. neys were divided and separated from the The mean values were analyzed statisti- adrenal glands. The renal pedicles were tied cally by ANOVA, with the level of signifi- with 4-0 polyglycolic acid thread and both cance set at P<0.05. kidneys were removed. Hemostasis was care- fully revised and the abdominal cavity was Results closed in two layers with 2-0 polyglycolic acid thread. Table 1 shows that plasma urea, creati- On the third postoperative day, all ani- nine and potassium concentrations were mals (groups I, II, and III) received an intra- higher in groups II and III than in group I venous injection of 99mTc sulfur colloid (1 (P<0.05). These levels were higher in group ml/kg) through the femoral vein, and were II than in group III. Plasma sodium concen- killed 30 min later by an inhalatory ether trations were lower in groups II and III than overdose. Blood samples (4 ml) were col- in group I (P<0.05). These levels were lower lected from the vena cava for the assessment in group II than in group III. of plasma urea (enzymatic test), creatinine Table 2 presents the mean values of arte- (colorimetric test), sodium and potassium rial gasometry for the three groups. There (Ise selective electrode) concentrations. was no significant difference between groups Samples of liver, spleen and lung (2 cm I and III. The presence of compensated meta- each) were obtained and a 2-cm blood clot was also collected. Each of these samples Table 1. Plasma urea, creatinine, sodium and potassium concentrations of rats with was introduced into a small plastic cup and renal and postrenal failures. precisely weighed. Radioactivity measure- ments were verified by introducing the cups Parameters Group I Group II Group III (Control) (Ureter ligature) (Nephrectomy) with the samples into a gamma-camera pin- hole collimator. Radioactivity was assessed Urea (mg/dl) 40.60 ± 6.54 686.20 ± 62.69* 665.60 ± 31.36* per gram of tissue. The total amount of ra- Creatinine (mg/dl) 0.52 ± 0.05 10.02 ± 1.96* 9.12 ± 0.25* + dioactivity injected into each animal was Sodium (mmol/l) 141.00 ± 1.86 123.96 ± 3.72* 129.34 ± 2.27* Potassium (mmol/l) 3.03 ± 0.37 9.32 ± 1.33*+ 7.42 ± 1.20* considered to be 1. Based on this value, the radioactivity determined in each organ was *P<0.05 compared to control; +P<0.05 compared to group III (ANOVA test). proportional to “1”. An extra group of nine rats was studied in order to verify the presence of acidosis in Table 2. Arterial gasometry of rats with renal and postrenal failures. animals with renal and postrenal failures. The Parameters Group I Group II Group III animals were divided into three groups (N = (Control) (Ureter ligature) (Nephrectomy) 3): group I - control (healthy animals - no procedures), group II - ligature of both ureters, pH 7.356 ± 0.031 7.318 ± 0.05 7.332 ± 0.083 pCO2 (mmHg) 41.567 ± 10.169 20.37 ± 8.21* 37.600 ± 11.692 and group III - bilateral nephrectomy. HCO3 (mmol/l) 22.433 ± 3.988 10.43 ± 4.86* 18.967 ± 2.815 Blood samples (4 ml) were collected by Base excess (mmol/l) -2.400 ± 2.615 -14.07 ± 6.09* -5.967 ± 2.255 abdominal aorta puncture for arterial gasom- *P<0.05 compared to control (ANOVA test). etry. This procedure was carried out under

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bolic acidosis was observed in group II when quent anemia of the organ. This picture is compared with group I (P<0.05). There was compatible with mild to moderate early hy- no significant difference between groups II dronephrosis (Figure 1). and III. Groups I and II did not present important The proportional and real mean radioac- morphological alterations as far as the spleen tivity values in each sample (liver, spleen, is concerned. Chronic and relatively intense lung and blood clot) are presented in Table 3. congestion was observed in group III. The animals of group II showed a lower In group I, histology of the liver showed level of radioactivity in the spleen (P = moderate to diffuse vacuolar or hydropic 0.000009) and lung than the control group. damage to the hepatocytes and small areas of However, the animals of group II had a necrosis with focal collapse of trabeculae. higher level of radioactivity in the liver (P = The liver of groups II and III presented 0.000006) compared with the control group. diffuse steatosis. In group I, histology of The level of radioactivity in the blood clot the lung did not show any important alter- was not different from the control group. ations. In groups II and III, small focuses of The animals of group III showed a lower discrete bronchopneumonia were observed level of radioactivity in the spleen (P<0.0006) (Figure 1). than the control group and a higher level in the liver, lung and blood clot than the control Discussion group, although the difference was significant only for the blood clot (P<0.04). Renal failure is characterized by impor- Group II presented a lower level of radio- tant hydroelectrolyte alterations and the ac- activity in the spleen, lung and blood clot, cumulation of nitrogen compounds. Patients and higher levels in the liver compared to with this syndrome present frequent infec- group III (P<0.03). tions and are usually susceptible to a high Histologically, group I presented moder- rate of sepsis (5). In our study, the acidosis, ate focal active pyelonephritis in one kidney the high level of urea, creatinine and potas- sample. The other samples did not present sium as well as the low level of sodium in any important alterations. Group II presented plasma confirmed the presence of renal fail- irregular, mild to moderate dilation of the ure. The group submitted only to ureter liga- renal tubules, tubular epithelium atrophy with ture had more severe electrolytic disturbances the presence of hyaline casts inside the distal probably due to the maintenance of the kid- tubules, capillary compression and conse- neys affected by urinary retention. This con-

Table 3. The proportional and real values of radioactivity (99mTc sulfur colloid - 110 mBq) in the mononuclear phagocytic system organs and blood of rats with renal and postrenal failures.

Samples Group I (Control) Group II (Ureter ligature) Group III (Nephrectomy)

Proportional Real (mBq/g) Proportional Real (mBq/g) Proportional Real (mBq/g)

Liver 0.599 ± 0.030 65.82 ± 3.29 0.962 ± 0.016* 105.51 ± 1.76* 0.625 ± 0.305+ 68.75 ± 33.55+ Spleen 0.345 ± 0.039 37.92 ± 4.29 0.008 ± 0.004* 0.98 ± 0.44* 0.122 ± 0.073*+ 3.42 ± 8.03*+ Lung 0.050 ± 0.028 5.54 ± 3.08 0.023 ± 0.015 2.63 ± 1.64 0.083 ± 0.019+ 9.13 ± 2.09+ Blood clot 0.004 ± 0.002 0.44 ± 0.22 0.003 ± 0.001 0.33 ± 0.11 0.017 ± 0.01*+ 1.87 ± 1.10*+

Radioactivity was assessed per gram of tissue. The total amount of radioactivity for all samples from each animal was considered to be 1. Based on this value, the radioactivities determined were proportional to “1”. *P<0.05 compared to control; +P<0.05 compared to group II (ANOVA test).

Braz J Med Biol Res 34(9) 2001 Influence of renal failure on phagocytic function 1173 dition may have contributed to the higher electrolytic alteration in this group. A Previous studies on diabetic patients have suggested a possible interference of ketoacidosis with monocyte receptors, provoking functional disturbances in these cells. Lactic acid interferes with tumor necrosis factor, influencing the defense mechanisms (11- 13). In the present investigation we assessed the presence of acidosis as a factor able to complicate the acute renal failure and to interfere with the mononuclear phagocytic system. Since the metabolic acidosis of our animals was compensated, a possible interference of this disturbance was not taken into consideration. The blood clot radioactivity indicates the rate of sulfur colloid in the circulation fol- B lowing its intravenous injection. An elevated radioactivity suggests the reduction of clearance by the reticuloendothelial system, which has been reported to be provoked at least in part by phagocytic cell inhibition or opsonin depletion (14). In our study, both the renal and postrenal groups presented decreased spleen phagocytosis indicated by the reduction of 99mTc sulfur colloid capture by the cells of the mononuclear phagocytic system. It may be proposed that this blockade does not depend on the presence of the kidney since the alterations occurred in both groups. Its exact mechanism remains to be investigated. Based on the literature, we may ascribe to the spleen C an early filtering role. Following renal failure the macrophage functions reached their limit or were impaired and consequently foreign circulating bodies such as colloids

Figure 1. Histological sections from rats submitted to ligature of both ureters (A) and ligature of both ureters plus nephrectomy (B and C). A, Renal medullar tissue presenting mild dilation of tubules and atrophy of the tubular epithelial cells. B, Hepatic parenchyma showing hepatocellular steatosis. C, Pulmonary parenchyma presenting small alveolar focuses of inflammatory cell infil- tration. Hematoxylin and eosin stain. Magnification 200X.

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were less removed than they would be under found in the spleen of nephrectomized rats normal conditions. However, we do not have was not specific and therefore did not provide enough data to propose colloid retention due enough data to explain its physiopathology. to renal failure. It is known that patients with renal failure It is known that the liver, as the most are more susceptible to pneumonia. The fo- important organ in the reticuloendothelial cal bronchopneumonia found in all groups system, is able to increase its phagocytic role suggests a possible role of the reticuloendo- when necessary, enhancing colloid uptake. thelial system in this susceptibility. The efficacy of this process probably pre- The results of the present study suggest vented the necessity of other organs to in- that renal and postrenal failures interfere crease their phagocytic function (15-17). with blood clearance of the colloid by the We did not find any data in the literature mononuclear phagocytic system. to help us understand the differences in phagocytic function in the presence or ab- Acknowledgments sence of the kidneys. Further investigations are necessary to obtain more information The authors gratefully thank Jair Pimenta about this phenomenon. Histology showed Oliveira, M.D., Francisco Danilo Paula, B.S., alterations usually found in the morphology and the Laboratory of Clinical Pathology of of hydronephrosis due to urinary retention in the University Hospital, Federal University the group submitted to ureter ligature. The of Minas Gerais. We thank Risa Andrade histological picture of chronic congestion Sousa for revising the English text.

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