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ω‐Agatoxin‐IVA‐sensitive calcium channels in bovine chromaffin cells
Author(s) -
Albillos Almudena,
García Antonio G.,
Gandía Luis
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80815-c
Subject(s) - chromaffin cell , channel blocker , dihydropyridine , chemistry , voltage dependent calcium channel , biophysics , calcium channel , calcium channel blocker , t type calcium channel , calcium , adrenal medulla , endocrinology , biology , catecholamine , organic chemistry
A large component of the whole‐cell currents through Ca 2+ channels in bovine adrenomedullary chromaffin cells has been shown to be insensitive to both L‐type and N‐type Ca 2+ channel Mockers, suggesting the existence of a third type of Ca 2+ channel. In the present paper, ω‐agatoxin‐IVA (AgTx), a selective blocker of P‐type Ca 2+ channels in mammalian neurons, has been used to investigate the presence of this subtype of Ca 2+ channel in bovine chromaffin cells. Barium currents ( I Ba ) through Ca 2+ channels were recorded in whole‐cell patch‐clamped bovine chromaffin cells. I Ba was blocked by AgTx in a dose‐dependent and irreversible manner. At the maximal concentration used (1 μM), AgTx inhibited T Ba by 49.5 ± 3%. Such a blockade was also present when bovine chromaffin cells were pretreated with 10 μM fumidipine, a novel 1,4‐dihydropyridine L‐type channel blocker, and after treatment with 1 μM of the N‐type channel blocker, ω‐conotoxin GVIA (CgTx). A combination of these three types of Ca 2+ channel blockers suppressed the macroscopic Ba 2+ currents by 88%. We conclude that bovine chromaffin cells, in addition to N‐ and L‐type Ca 2+ channels, possess a P‐like component in their whole‐cell currents through the Ca 2+ channels.