Different contributions of l- and q-type ca 2+ channels to ca2+
signals and secretion in chromaffin cell subtypes.
Lomax, Richard B., Pedro Michelena, Luc[acute]ia N[acute]u[tilde]nez,
Javier Garc[acute]ia-Sancho, Antonio G. Garc[acute]ia, and Carmen
Montiel.
Departamento de Farmacolog[acute]ia y Terap[acute]eutica, Facultad
de Medicina, Universidad Aut[acute]onoma de Madrid, c/ Arzobispo
Morcillo 4, 28029 Madrid, Spain, Servicio de Farmacolog[acute]ia
Cl[acute]inica and Instituto de Gerontolog[acute]ia, Hospital de la
Princesa, c/Diego de Le[acute]on, 62, 28006 Madrid, Spain and
Instituto de Biolog[acute]ia y Gen[acute]etica Molecular, Universidad
de Valladolid y CSIC; Departamento de Bioqu[acute]imica,
Biolog[acute]ia Molecular y Fisiolog[acute]ia, Facultad de Medicina,
47005 Valladolid, Spain
APStracts 3:0258C, 1996.
This study investigated the contribution of different subtypes of
voltage-dependent Ca2+ channels to changes in cytosolic Ca2+,
[Ca2+]i, and secretion in noradrenergic and adrenergic bovine
chromaffin cells. In single immunocytochemically identified
chromaffin cells [Ca2+]i increased transiently during high K+
depolarization. Furnidipine and Bay K 8644, L-type Ca2+ channel
blocker and activator respectively, affected more the [Ca2+]i rise in
noradrenergic than in adrenergic cells. In contrast, the Q-type Ca2+
channel blocker w-conotoxin MVIIC inhibited more the [Ca2+]i rise in
adrenergic cells. 30 nM w-agatoxin IVA, which blocks P-type Ca2+
channels, affected little the [Ca2+]i signal. The N-type Ca2+ channel
blocker w-conotoxin GVIA inhibited similarly the [Ca2+]i rise in both
cell types. The effects of furnidipine, Bay K 8644 and w-conotoxin
MVIIC on K+-evoked norepinephrine and epinephrine release paralleled
those on [Ca2+]i signals. However, w-conotoxin GVIA and 30 nM w
-agatoxin IVA did not affect the secretion of either amine. The data
suggest that in the bovine adrenal medulla the release of epinephrine
and norepinephrine are preferentially controlled by Q- and L-type
Ca2+ channels respectively. P- and N-type Ca2+ channels do not seem
to control the secretion of either catecholamine.
Received 20 May 1996; accepted in final form 24 July 1996.
APS Manuscript Number C277-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996