ISSN:1420-4096    

DOI:10.1159/000173108

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

We have examined the effects of erythrocytes on the function and morphology of isolated rat kidneys perfused with a physiological concentration of bovine albumin (45 g/l). (1) In kidneys perfused without red cells, renal vascular resistance (RVR) was low (4.2 ± 0.3 mm Hg/ml/min/g), fractional sodium excretion (FeNa) was high (14.5 ± 1.8%) and concentrating ability impaired (maximum urine osmolality 343 ± 4 mmol/kg). The erythrocyte-free kidney also developed necrosis of the cells of the medullary thick ascending limb (mTAL). (2) Erythrocytes at a hematocrit of 4–6% did not alter RVR but prevented ischemic changes in the mTAL and reduced FeNa to 9.4 ± 0.03%. Concentrating ability was not improved by a hematocrit of 4–6% despite the presence of a morphologically normal mTAL. (3) At a hematocrit of 40–45%, RVR was increased (to 11.2 ± 0.4 mm Hg/ml/min/g) and FeNa was further lowered to 3.5 ± 0.6%. Also, urinary concentrating ability was markedly improved (maximum urine osmolality 640 ± 35 mmol/kg). (4) The isolated perfused kidney (IPK) at a hematocrit of 40–45% was able to autoregulate renal perfusate flow rate of GFR but auto-regulation was incomplete. A 50% increase in perfusion pressure from 100 to 150 mm Hg increased renal perfusate flow rate and GFR 27 and 29%, respectively. Thus the IPK is not able to autoregulete as efficiently as the kidney in vivo, even in the presence of red cells at a nor

ISSN:1420-4096    

DOI:10.1159/000173109

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The possible mediation of the endogenous prostaglandin and kallikrein-kinin systems of changes in renal function induced by furosemide was studied in anesthetized rats. Increasing doses of furosemide infusion (0.03, 0.1, and 0.3 mg/kg/min) caused dose-related diuresis, natriuresis, kaliuresis, and decreased renal blood flow and urinary osmolality without any significant changes in mean arterial blood pressure. Pretreatment with the prostaglandin synthetase inhibitor indomethacin resulted in marked reduction of the water and sodium excretion induced by furosemide. It also blunted renal vasoconstriction and renin release by furosemide, but the glomerular filtration rate was not affected. Pretreatment with aprotinin, a kallikrein inhibitor, failed to affect the renal response to furosemide. The results indicate that the renal prostaglandin system, but not the kallikrein-kinin system, participates in the effect of furosemide on renal functions mainly through electrolyte transport inhibition in the renal tubule.

ISSN:1420-4096    

DOI:10.1159/000173110

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

To test the possibility that adenosine may be involved in a urine concentrating mechanism, effects of 1-phenylisopropyladenosine (PIA) on cyclic AMP levels have been examined in medullary thick ascending limb (mTAL) and medullary collecting duct (MCD) isolated from the rat. Low and high doses of PIA did not alter basal cyclic AMP levels in both segments. However, PIA depressed vasopressin-dependent cyclic AMP production in MCD in a dose-dependent manner: this effect of PIA was maximum at 10-6M. 8-Phenyltheophylline, a competitive inhibitor for adenosine receptor, completely abolished this inhibitory effect of PIA. This finding may suggest an existence of adenosine receptor on the MCD. In mTAL, PIA also suppressed vasopressin-mediated cyclic AMP generation. The present study shows an interaction between PIA and vasopressin in both MCD and mTAL. This interaction may contribute in part to urinary-concentrating disturbance in renal ischemia.

ISSN:1420-4096    

DOI:10.1159/000173111

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

We examined the release of vasopressin and the renal response to exogenous vasopressin before and during desoxycorticosterone acetate (DOCA) administration in the dog. As treatment with DOCA produced potassium loss, urine volume increased, urinary osmolality decreased, and urinary PGE2 tended to increase. The increase in urine volume was accompanied by increases in serum sodium, in plasma osmolality and in plasma arginine vasopressin. The threshold for vasopressin release measured during polyuria was higher than control but the rate of vasopressin release was unchanged. The DOCA-induced polyuria was not affected by treatment with vasopressin which further increased plasma vasopressin. Treatment with indomethacin which corrected the increase in urinary PGE2 excretion but not the hypokalemia, restored the renal responsiveness to vasopressin, decreased the secretion of vasopressin, and corrected the polyuria and the hypernatremia. These findings suggest that DOCA-induced polyuria is attributable to a decrease in renal responsiveness to vasopressin which may be mediated in part by an increase in the renal synthesis of prostaglandins.

ISSN:1420-4096    

DOI:10.1159/000173112

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

In 22- to 26-day-old beagle puppies, just after superficial nephrons have begun to function, the single nephron glomerular filtration rate is extremely low (6.7nl·min-1) approximating a tenth of the adult value (5 7 nl min-1) even though blood pressure is as high as 90 mm Hg. Glomerular vascular resistance is almost six times the value found in the adult dog (1.8 vs. 0.32 mm Hg· ml-1 min), this increase being mainly due to a rise in afferent (80%) rather than in efferent (20%) resistance. The glomerulus, having only recently started to function, is characterized by filtration pressure equilibrium, a phenomenon atypical of superficial glomeruli in the adult dog. These findings favor the concept that a low glomerular blood flow rate might be the main cause of the very low SNGFR in the new glomeruli, although some contribution of an altered ultrafiltration coefficient cannot be exclude

ISSN:1420-4096    

DOI:10.1159/000173113

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The nephrotoxic effect of cisplatin (5 mg/kg i.v.) was evaluated in 8 dogs 48–72 h after administration. The lithium clearance method was used for assessing the absolute and fractional reabsorption rates of sodium and water in proximal as well as in more distal segments of the total nephron population, before and during saline loading (infusion of 5 ml/kg of isotonic saline i.v.). Histological examinations of the kidney biopsies were used to evaluate the degree of renal tissue injury. During 48–72 h after administration of cisplatin blood urea nitrogen and plasma creatinine increased significantly from 3.9 ± 0.2 to 11.7 ± 1.4 mmol/l and 96 ± 3 to 178 ± 10 µmol/l, respectively. Mean values of renal blood flow, glomerular filtration rate, filtration fraction and lithium clearance in cisplatin-treated animals (143 ± 14 ml/min, 10.7 ± 1.1. ml/min, 0.14 ± 0.01 and 6.3 ± 0.6 ml/min, respectively) were significantly lower than in 6 control animals (212 ± 8 ml/min, 49.0 ± 2.0 ml/min, 0.36 ± 0.01 and 10.1 ± 1.3 ml/min, respectively). In contrast, urinary excretion rates of sodium, potassium and water were significantly higher, while fractional as well as absolute proximal and distal reabsorption rates were significantly lower in cisplatin-treated animals compared to controls. Saline loading caused an increase in the output of tubular fluid from the proximal tubules (lithium clearance) in the cisplatin-treated animals, while the fractional distal reabsorption rate of sodium decreased significantly. The histological changes are in agreement with the physiological data which point to the proximal tubules as the more severely damaged segment. In conclusion, the depressed renal function 48–72 h after administration of cisplatin can be attributed to impairment of proximal as well as distal tubular reabsorptive capacities associated with increased renal vascular resistance. The polyuria seems to be due to impaired reabsorption rates in the distal nephron segments, which will affect the conce

ISSN:1420-4096    

DOI:10.1159/000173114

出版商:S. Karger AG    

年代:1987

数据来源: Karger