Functional evidence for l-type ca2+ channels controlling adrenal
catecholamine release induced by angiotensin ii in vivo.
Martineau, Daniel, Richard Briand, and Nobuharu Yamaguchi.
Groupe de recherche sur le syst[grave]eme nerveux autonome,
Facult[acute]e de pharmacie, Universit[acute]e de Montr[acute]eal,
C.P. 6128, Centreville, Montr[acute]eal, QC, H3C 3J7, Canada,
Bristol-Myers Squibb (Canada), 2365 ch. C[circumflex]ote-de-Liesse,
Montr[acute]eal, QC, H4N 2M7, Canada
APStracts 3:0234R, 1996.
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 in
anesthetized dogs. Plasma catecholamine concentrations in adrenal
venous and aortic blood were determined by an HPLC-electrochemical
method. In the first series of experiments, repeated infusions of
BAY-K 8644 locally administered into the left adrenal gland with an
interval of 15 min resulted in significant and reproducible increases
in adrenal catecholamine secretion. Nifedipine, similarly
administered 5 min prior to BAY-K 8644, diminished BAY-K 8644-induced
catecholamine secretion in a dose-dependent manner and completely
blocked the catecholamine response with the highest dose tested. In
the second series, locally infused angiotensin II resulted in a
significant increase in adrenal catecholamine secretion. The maximum
catecholamine response to angiotensin II was attenuated by
approximately 65% in the presence of nifedipine with the dose that
abolished the BAY-K 8644-induced catecholamine release. This
inhibition by nifedipine remained unchanged in the presence of
additional -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
angiotensin II-induced adrenal catecholamine secretion, suggesting
the existence of another mechanism. However, -conotoxin-sensitive N
-type Ca2+ channels are unlikely to be functionally involved in
postsynaptic mechanisms mediating adrenal catecholamine secretion in
response to exogenous angiotensin II under in vivo conditions.
Received 28 September 1995; accepted in final form 30 May 1996.
APS Manuscript Number R609-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96