AJP - Renal Physiology, Vol 253, Issue 5 1063-F1067, Copyright © 1987 by American Physiological Society
Adrenal medullary regulation of rat renal cortical adrenergic receptors
P. R. Sundaresan, M. M. Guarnaccia and J. L. Izzo Jr
Department of Pharmacology, University of Rochester Medical Center, New York 14642.
The role of the adrenal medulla in the regulation of renal cortical
adrenergic receptors was investigated in renal cortical particulate
fractions from control rats and rats 6 wk after adrenal demedullation. The
specific binding of [3H]prazosin, [3H]rauwolscine, and
[125I]iodocyanopindolol were used to quantitate alpha 1-, alpha 2-, and
beta-adrenergic receptors, respectively. Adrenal demedullation increased
the concentration of all three groups of renal adrenergic receptors;
maximal number of binding sites (Bmax, per milligram membrane protein) for
alpha 1-, and alpha 2-, and beta-adrenergic receptors were increased by 22,
18.5, and 25%, respectively (P less than 0.05 for each). No differences
were found in the equilibrium dissociation constants (KD) for any of the
radioligands. Plasma corticosterone and plasma and renal norepinephrine
levels were unchanged, whereas plasma epinephrine was decreased 72% by
adrenal demedullation (P less than 0.01); renal cortical epinephrine was
not detectable in control or demedullated animals. Our results suggest
that, in the physiological state, the adrenal medulla modulates the number
of renal cortical adrenergic receptors, presumably through the actions of a
circulating factor such as epinephrine.
