ISSN:
1432-2013
Keywords:
Key words Adrenal chromaffin cell
;
Ca2+ current
;
Ca2+ channel
;
Nifedipine
;
ω-Conotoxin GVIA
;
ω-Agatoxin IVA
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The effects of nifedipine, ω-conotoxin GVIA (ω-CgTx) and ω-agatoxin IVA (ω-AgTx) on Ca2+ currents, a 60-mM-K+-induced increase in intracellular Ca2+ concentration ([Ca2+]i) and catecholamine secretion were examined to clarify the subtypes of Ca2+ channels in cultured adrenal chromaffin cells from the pig. Nifedipine, ω-CgTx, and ω-AgTx inhibited Ca2+ currents in a dose-dependent manner, suggesting the presence of L-, N- and P-type Ca2+ channels. The maximal doses of nifedipine (10 μM), ω-CgTx (1 μM), and ω-AgTx (0.1 μM) inhibited Ca2+ currents to 85%, 22%, and 94% of control currents, respectively. The inhibitory effects of these three blockers were observed in the same cell, indicating that at least three subtypes of Ca2+ channels are present in porcine chromaffin cells. The increase in [Ca2+]i and catecholamine secretion induced by 60 mM K+ were inhibited equally by nifedipine (10 μM) and ω-CgTx (1 μM), but not by ω-AgTx (0.1 μM). These results suggest that L-, N- and P-type Ca2+ channels are present in porcine adrenal chromaffin cells, and that the major pathways of Ca2+ entry evoked by a high concentration of K+ are L- and N-type Ca2+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050381
