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Am J Physiol Regul Integr Comp Physiol 271: R1713-R1719, 1996;
0363-6119/96 $5.00
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AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 6 1713-R1719, Copyright © 1996 by American Physiological Society

ARTICLES

Functional evidence for L-type Ca2+ channels controlling ANG II-induced adrenal catecholamine release in vivo

D. Martineau, R. Briand and N. Yamaguchi
Groupe de Recherche sur le Systeme Nerveux Autonome, Faculte de Pharmacie, Universite de Montreal, Quebec, Canada.

The aim of the present study was to investigate the functional involvement of L- and/or N-type Ca2+ channels in adrenal catecholamine secretion in response to exogenous angiotensin II (ANG II) in anesthetized dogs. Plasma catecholamine concentrations in adrenal venous and aortic blood were determined by a high-performance liquid chromatography-electrochemical method. In the first series of experiments, repeated infusions of BAY K 8644 locally into the left adrenal gland at 15-min intervals resulted in significant and reproducible increases in adrenal catecholamine secretion. Nifedipine, similarly administered 5 min before BAY K 8644, diminished BAY K 8644-induced catecholamine secretion in a dose-dependent manner and completely blocked the catecholamine response at the highest dose tested. In the second series of experiments, local infusion of ANG II resulted in a significant increase in adrenal catecholamine secretion. The maximum catecholamine response to ANG II was attenuated by approximately 65% in the presence of nifedipine at the dose that abolished the BAY K 8644-induced catecholamine release. This inhibition by nifedipine remained unchanged in the presence of omega-conotoxin. The present study shows that dihydropyridine-sensitive L-type Ca2+ channels are operative in the adrenal medulla of the dog in vivo. The results indicate that the L-type Ca2+ channels are only partially implicated in the local regulation of ANG II-induced adrenal catecholamine secretion, suggesting the existence of another mechanism. However, omega-conotoxin-sensitive N-type Ca2+ channels are unlikely to be functionally involved in postsynaptic mechanisms mediating adrenal catecholamine secretion in response to exogenous ANG II under in vivo conditions.


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G. Geng, R. Gaspo, F. Trabelsi, and N. Yamaguchi
Role of L-type Ca2+ channel in PACAP-induced adrenal catecholamine release in vivo
Am J Physiol Regulatory Integrative Comp Physiol, October 1, 1997; 273(4): R1339 - R1345.
[Abstract] [Full Text] [PDF]


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