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Effects of Acute Ureteral Obstruction on Glomerular Hemodynamics in Rat Kidney

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Effects of Acute Ureteral Obstruction on Glomerular Hemodynamics in Rat Kidney View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Kidney International, Vol. 12 (1977), pp. 403 —411 Effects of acute ureteral obstruction on glomerular hemodynamics in rat kidney ANTONIO DAL CANTON, R0D0LF0 STANZIALE, ARIBERTO CORRADI, VITT0RI0 E. ANDREUCCIand LUIGI MIGONE Secondo Clinica Medico, University of Parmo, and Division of Nephrology, Second Faculty of Medicine, University of Naples, Italy Effects of acute ureteral obstruction on glomerular hemodynam- 59,3 4,0mm Hg) et de AABF (de 130,3 59,1is 144,2 69,0 irs in rat kidney. In order to study the effects of acute ureteral nllmin) secondaires is La chute de R. Ces resultats démontrent que obstruction on glomerular hemodynamics, glomerular hydrostatic SNGFR est maintenu au debut dune obstruction uréterale totale capillary pressure (PG),pressurein the first-order peritubular capil- grisce a Ia dilatation de l'artCriole afferente. laries (EAP), and intratubular pressure (PT) were directly mea- sured in superficial nephrons of Munich-Wistar rats by micropunc- tare with a servo-nulling device, in control conditions and one to As yet, no measurement of glomerular filtration two hours after ureteral ligation. Single nephron filtration fraction rate in the whole kidney (GFR) nor in the single (SNFF) was calculated from arterial and peritubular blood protein nephron (SNGFR) early after ureteral obstruction concentration. SNGFR was measured by conventional micro- puncture techniques in control conditions and was calculated from has been reported. It has been postulated, however, efferent arteriole blood flow (EABF) and SNFF during ureteral that during ureteral obstruction intrarenal hemody- obstruction. EABF was obtained by timed complete collection of blood from superficial efferent arterioles. Afferent arteriole blood namic adjustments occur, maintaining ultrafiltration flow (AABF) and resistance of affcrcnt (Ra) and efferent arterioles despite a significant rise in intratubular pressure. (Re) were calculated from conventional equations. Ureteral Blood flow across single glomerular arterioles usu- obstruction markedly increased PT from 12.9 1.4 to 36.8 6.1 ally is determined indirectly by micropuncture from (sD) mm Hg. The fall in SNGFR (from 23.3 6.4 to 17.95.2 [SD] ullmin) was blunted by thc rise in G(from45.5 3.6 to 59.34.0 SNGFR, single nephron filtration fraction (SNFF), [sri] mm Hg) and AABF (from 130.3 59.1 to 144.2 69.0 [sri] and systemic blood hematocrit. Clearance tech- nl/min), secondary to a fall in Ra. These results demonstrate that niques, however, might be unsuitable for SNGFR SNGFR is maintained early after complete ureteral obstruction because of afferent arteriole dilatation. measurements during ureteral obstruction, since they require a tubular fluid collection, for which Effets de l'obstruction urétérale aigué stir l'hémodynamique release of the obstruction would take place. Alterna- glomérulaire chez le rat. Afin d'etudier les effets de l'obstruction urétéraie aigue sur l'hémodynamique glomérulaire, [a pression tively, efferent arteriole blood flow (EABF) can be hydrostatique glomérulaire (PG), [a pression dans les capillaires directly measured by timed complete collection of péritubulaires de premier ordre (EAP), et la pression intra-tubu- blood from the efferent arteriole at its welling point laire (PT) ont été mesurées directement dans des néphrons superfi- ciels de rats Munich-Wistar, par microponctions, au moyen d'un on the kidney surface. From efferent arteriole plas- systéme asservi, dans les conditions basales et aprés deux heures ma flow (EAPF, derived from EABF) and SNFF, de ligature urétérale. La fraction de filtration des néphrons indivi- SNGFR can be calculated also according to the duels (SNFF) a été calculée is partir des concentrations de protéine du sang péri-tubulaire. SNGFR a été mesuré par les techniques equation Li]: habitueiles de microponction dans les conditions basales et a été calculé is partir du debit sanguin dans l'artériole efférente (EABF) et SNFF au cours de l'obstruction urétérale. EABF a été obtenu SNGFR = —EAPF. (1) par un recueil complet et minute du sang des arterioles efférentes 1—SNFF superficielles. Le debit sanguin dans l'artdriole afferente et Ia résistance des arterioles afferente (Ra) et efferente (Re) ont été In this way, no tubular collection is required, SNFF calculds au moyen des equations habituelles. L'obstruction uré- térale a augmenté PT de façon importante de 12,9 1,4 sri is 36,8 being calculated from protein concentration in blood 6,1 mm Hg. La chute de SNGFR (de 23.3 6,4 is 17.9 5,2nIl samples collected from the efferent arteriole and mm) est masquée par 1' augmentation de P (de 45,5 [sri] 3,6 is from a femoral artery [2]. Obviously, direct mea- surement of EABF is valid only if the efferent arteri- Received for publication December 3, 1976; and in revised form July 5, 1977. oles from the outermost glomeruli have a straight © 1977, by the International Society of Nephrology. unbranched pathway to the kidney surface, as dem- 403 404 Canton et a! onstrated in rats of the Sprague-Dawley and Wistar As soon as the blood reached the pipette tip, a slight strain [1, 3—51. aspiration started the blood collection; the oil into Thepresent study was undertaken to evaluate the the peritubular capillaries distal to the pipette tip glomerular hemodynamics and to measure SNGFR provided the best proof of complete collection and in the rat kidney one to two hours after ureteral prevented retrograde flow of blood [1]. At the end of ligation. collection, the pipette was withdrawn, and a drop of clear oil was aspirated into the tip to prevent evapo- Methods ration [2]. All of the present micropuncture experiments At the end of micropuncture collections, a catheter were carried out in a mutant strain of Munich-Wistar (PE-50) was inserted into the abdominal aorta, and rats having glomeruli on the kidney surface accessi- its tip was located at the level of the renal arteries ble to direct micropressure measurements [2]. [2]. The mesenteric arteries and the aorta just above Twenty-five non-fasted female rats, weighing 150 the renal arteries were then clamped, and Neoprene® to 200 g, were anesthetized i.p. with sodium pento- (Latex 842A, Dupont de Nemours Company) was barbital (Nembutal ®,60mg/kg of body wt) and were rapidly injected through the aortic catheter for mak- prepared for micropuncture. as previously described ing a cast of the renal vascular tree. The left kidney [6,7]. After the surgical preparation, an i.v. mfu- was immediately removed and rapidly frozen in liq- sion of bicarbonate-saline solution (sodium chloride, uid nitrogen; 1001k-thick sections were made and 110 mEq/liter; sodium bicarbonate, 28 mEq/liter; dipped into 10% hydrochloric acid at 37°C for 15 to potassium chloride, 5 mEq/liter) containing chemical 20 mm for maceration. Microdissection of 100 effer- (nonisotopic) inulin (10%) was begun at an infusion ent arterioles of the outermost glomeruli was then rate of 0.02 mi/mm, and was maintained thereafter. performed [2]. Sixty minutes were allowed for equilibration before B)Rats with ureteral ligation, inten rats, the left starting micropuncture collections and micropressure ureter was ligated approximately one centimeter measurements [8]. Fifteen of these animals were below the renal pelvis. After one hour, timed collec- used for validating the method for SNGFR measure- tions of tubular fluid and of efferent blood were ment in Munich-Wistar rats; the other ten rats were performed for SNGFR measurements, as previously used for studying the glomerular hemodynamics dur- described. ing ureteral obstruction and for postobstructive Ureteralobstruction studies. Inten rats, the fol- studies. lowing measurements were made in control condi- Studiesfor validation of the method for SNGFR tions: a) GFRs of both kidneys were measured. Two measurements: A) Normal rats. Infive rats, SNGFR 30-mm clearance periods were performed. Urine was was 1)measuredby conventional techniques and 2) collected under mineral oil from the left ureter calculated from EAPF and SNFF values. For through a PE-lO catheter and from the bladder (for SNGFR measurement by conventional techniques, the right kidney) through a PE-50 catheter. Arterial timed complete collections of proximal tubular fluid blood samples were obtained from the femoral artery were performed with sharpened micropipettes (5to at the beginning and the end of each clearance peri- 8, O.D.) filled with colored mineral oil. After inser- od. b) SNGFR was measured by conventional tech- tion of the pipette tip into the tubule, an oil block (3 niques. Timed complete collections of proximal to 4 tubular diameters) was injected, and collection tubular fluid (without locating the puncture site along was started by gentle aspiration and spontaneously the tubule) were performed as described above. c) continued thereafter for at least three minutes [2, 8]. EABF was measured for calculating SNGFR from For SNGFR calculation from EAPF and SNFF, EAPF and SNFF. Timed complete collections of timed complete collections of blood were performed blood were performed from efferent arterioles of from efferent arterioles of superficial nephrons, uti- superficial nephrons at their welling points as lizing heparinized oil-filled micropipettes (12 to l5i, described above. d) Cortical hydrodynamic pres- O.D.).After the insertion of the pipette tip into the sures were measured. Glomerular capillary pressure largest peritubular capillary (the welling point), a (PG),pressurein the first-order peritubular capillaries small quantity of uncolored mineral oil was injected, (so-called efferent arteriole pressure, EAP), and displacing the blood within the capillary so that the hydrostatic pressure in proximal tubules or Bow- latter became clear; within a few seconds, blood man's capsule (PT) were directly measured with a flowing from the glomerulus to the efferent arteriole servo-nul ling pressure-measuring system, as previ- displaced the injected oil so that smaller oil columns ously described [7, 9j, and recorded simultaneously filled the outwardly radiating peritubular capillaries.
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