Role of bradykinin and kinin b2 receptors in the developmental
changes of renal hemodynamics in the neonatal rat.
El-Dahr, Samir S., Igor V. Yosipiv, Lynn Lewis, and Kenneth D.
Mitchell.
Departments of Pediatrics and Physiology, Tulane University School
of Medicine, New Orleans, Louisiana 70112
APStracts 2:0102F, 1995.
The present study was performed to evaluate the role of bradykinin,
acting via B2 receptors, in the developmental rise in renal blood
flow (RBF) and glomerular filtration rate (GFR) in the rat. Newborn
rats were chronically treated from birth with the kinin B2 receptor
antagonist HOE 140 (600 [mu]g/kg, s.c., q12h, N=9) or 0.9% saline
(N=7). Weanling rats (mean age 23 days) were anesthetized with
pentobarbital sodium (50 mg/kg i.p.) for measurements of mean
arterial pressure (MAP), GFR, and RPF estimated from PAH clearance
(ERPF). Outer cortical RBF (OCBF) was measured by laser Doppler
flowmetry. Baseline MAP was similar in HOE- and saline-treated rats
(96+/-4 vs. 97+/-4 mmHg). Also, baseline GFR (0.65+/-0.05 vs. 0.52+/
-0.08 ml/min/g) and ERPF (1.6+/-0.2 vs. 1.3+/-0.1 ml/min/g) were not
different in HOE- and saline-treated rats, respectively. Intravenous
infusion of 200 ng bradykinin did not change MAP or OCBF in HOE rats
but decreased MAP (-29+/-3%, p<0.05) and OCBF (-20+/-2%,
p<0.05) in controls. Infusion of 25 ng i.v. angiotensin II
increased MAP equally in both groups (-32+/-4%) and caused a similar
reduction in OCBF (-37+/-14 vs. -46+/-5%). The AT1 receptor
antagonist, losartan (10 mg/kg i.v.) decreased MAP equally in both
groups (-22+/-2%). However, AT1 blockade increased ERPF to 3.1+/-0.8
ml/min/g (p<0.05 vs. baseline) in saline but not in HOE rats
(1.9+/-0.4 ml/min/g). Kidney renin mRNA and angiotensin II contents
were not different in HOE vs. saline groups. The present findings
indicate that bradykinin is not a primary mediator of the
maturational rise in RBF or GFR in the rat. However, the data suggest
that under control conditions, angiotensin II, acting via AT1
receptors, counteracts the renal vasodilatory effects of endogenous
bradykinin in the developing kidney.
Received 1 December 1994; accepted in final form 1 June 1995.
APS Manuscript Number F425-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.