Premium
Differential Control of Tyrosine Hydroxylase Activation and Catecholamine Secretion by Voltage‐Operated Ca 2+ Channels in Bovine Chromaffin Cells
Author(s) -
O'Farrell Melanie,
Marley Philip D.
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.741271.x
Subject(s) - nitrendipine , chromaffin cell , catecholamine , tyrosine hydroxylase , adrenal medulla , chemistry , tyrosine 3 monooxygenase , voltage dependent calcium channel , endocrinology , medicine , dihydropyridine , biophysics , calcium , biology , dopamine
Contributions of L‐, N‐, and P/Q‐type voltage‐operated Ca 2+ channels to two responses of bovine adrenal chromaffin cells have been studied using the nonreceptor stimulus K + depolarization. Tyrosine hydroxylase activity and catecholamine secretion were both increased by K + over a similar concentration range and in a Ca 2+ ‐dependent manner. At a submaximal concentration of 20 m M K + , tyrosine hydroxylase activation was reduced by nitrendipine but unaffected individually by (±)‐Bay K 8644, ω‐conotoxin GVIA, ω‐agatoxin IVA, and ω‐conotoxin MVIIC. It was fully blocked by combined inhibition of L‐, N‐, and P/Q‐type channels. With a maximal concentration of 50 m M K + , tyrosine hydroxylase activation was unaffected by nitrendipine as well as by each of the other drugs on its own; however, it was reduced by 71% by combined inhibition of L‐, N‐, and P/Q‐type channels. In contrast, catecholamine secretion with both 20 and 50 m M K + was enhanced by (±)‐Bay K 8644, partially inhibited by nitrendipine and ω‐conotoxin MVIIC, and completely blocked by a combination of antagonists for L‐, N‐, and P/Q‐type channels. The results show that Ca 2+ entry through voltage‐operated Ca 2+ channels can differentially regulate distinct chromaffin cell responses and that this is an intrinsic property of the mechanisms by which Ca 2+ entry activates these responses. It is not dependent on the parallel activation of other signaling events by receptors.