AJP - Renal Physiology, Vol 248, Issue 1 128-F133, Copyright © 1985 by American Physiological Society
Renal alpha-adrenoceptors and sodium excretion in the dog
R. D. Fildes, G. M. Eisner, P. L. Calcagno and P. A. Jose
The purpose of this study was to characterize the age-dependent role of
alpha-adrenergic activity on renal vascular resistance (RVR) and renal
blood flow (RBF) and the role of alpha 2-receptors in sodium transport.
Intrarenal infusion of phentolamine in hydropenic anesthetized pups and
adult dogs increased RBF and glomerular filtration rate (GFR) only in pups.
The effect was most marked in the youngest pups (15.67 +/- 0.67 days). At
1.0 micrograms X kg-1 X min-1, phentolamine increased RBF from 1.38 +/-
0.04 to 1.64 +/- 0.04 ml X min-1 X g kidney wt-1 and GFR from 0.19 +/- 0.01
to 0.23 +/- 0.01 ml X min-1 X g kidney wt-1. Absolute (UNaV) and fractional
(FENa) sodium excretions increased in all animals, but mean percent
increases were greatest in adult dogs. Intrarenal yohimbine infusion in
adult dogs (10-100 micrograms X kg-1 X min-1) produced a dose-related
increase in UNaV and FENa without affecting RBF and GFR. UNaV increased
from 0.22 +/- 0.05 to 0.54 +/- 0.12 mueq X min-1 X g kidney wt-1 and FENa
increased from 0.32 +/- 0.05 to 0.63 +/- 0.06% at the dose of 100
micrograms X kg-1 X min-1. These studies confirm a modest role for
alpha-adrenoreceptors in the high RVR characteristic of newborn pups and
provide evidence for a role of alpha 2-adrenoceptors in the renal transport
of sodium; the extent of the contribution of renal alpha-adrenergic system
could not be tested in this experiment.
