AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 4 1034-R1042, Copyright © 1994 by American Physiological Society
Role of the atrial natriuretic peptide for adrenal regulation in the teleost fish Cyprinus carpio
W. Kloas, M. Reinecke and W. Hanke
Department of Zoology II, University of Karlsruhe, Germany.
The biological role of atrial natriuretic peptide (ANP) for the adrenal
tissue of the teleost fish Cyprinus carpio, the carp, was investigated
using in vitro autoradiography to study ANP binding sites,
immunohistochemistry to localize ANP-like peptides, and in vitro perifusion
to measure adrenal cortisol and catecholamine release. 125I-labeled rat
ANP-(99-126) [125I-rANP-(99-126)] binding was present in adrenal tissue
exhibiting positive cooperativity with a half-maximal binding concentration
(EC50) of 87 +/- 15 pM and a maximal binding capacity (Bmax) of 56 +/- 11
amol/mm2 (n = 3). 125I-rANP-(99-126) binding was competitively displaced by
unlabeled ANP analogues with an intact disulfide bridge showing a lower
affinity than the iodinated ligand. By the use of immunohistochemistry, ANP
immunoreactivity was found in the majority of the phenylethanolamine
N-methyl-transferase-immunoreactive, i.e., epinephrine-synthesizing cells.
In vitro, ANP elevated both basal and acetylcholine-stimulated cortisol
release by carp adrenal tissue, whereas adrenal catecholamines were
significantly affected only in acetylcholine-stimulated epinephrine
secretion. Thus ANP derived from the ANP-immunoreactive chromaffin cells of
the carp adrenal seems to act in an autocrine and/or paracrine manner on
steroidogenic interrenal and catecholaminergic chromaffin cells.
Furthermore, the study indicates that the ANP effects on fish catecholamine
and steroid release are reversed in mammals.
