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Inhibition of nicotinic responses of bovine adrenal chromaffin cells by the protein kinase C inhibitor, Ro 31–8220
Author(s) -
Marley Philip D.,
Thomson Kerrie A.
Publication year - 1996
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1996.tb16002.x
Subject(s) - bisindolylmaleimide , forskolin , endocrinology , protein kinase c , medicine , phorbol , protein kinase a , tyrosine hydroxylase , chromaffin cell , chemistry , biology , adrenal medulla , catecholamine , kinase , biochemistry , stimulation , dopamine
1 The effects of the protein kinase C inhibitor, Ro 31–8220, on the responses of cultured bovine adrenal chromaffin cells to nicotine, phorbol 12,13‐dibutyrate (PDBu) and K + have been investigated. 2 Tyrosine hydroxylase activity was measured in situ in intact cells by measuring 14 CO 2 evolved following the hydroxylation and rapid decarboxylation of [ 14 C]‐tyrosine offered to the cells. Secretion of endogenous adrenaline and noradrenaline was measured by use of h.p.1.c. with electrochemical detection. Cyclic AMP levels were measured in cell extracts by RIA. 3 Ro 31–8220 produced a concentration‐dependent inhibition of 300 nM PDBu‐stimulated tyrosine hydroxylase activity with an IC 50 of < 2 μ m and complete inhibition at 10 μ m . It had no effect on the responses to forskolin. 4 Ro 31–8220 produced a concentration‐dependent inhibition of 5 μ m nicotine‐stimulated tyrosine hydroxylase activity, adrenaline and noradrenaline secretion and cellular cyclic AMP levels, with an IC 50 of about 3 μ m and complete inhibition by 10 μ m . At concentrations up to 10 μ m , Ro 31–8220 had little or no effect on the corresponding responses to 50 mM K + . 5 A structural analogue of Ro 31–8220, bisindolylmaleimide V, that lacks activity as a protein kinase C inhibitor, had no effect up to 10 μ m on PDBu‐stimulated tyrosine hydroxylase activity or on nicotine‐stimulated cyclic AMP levels or noradrenaline secretion and only marginal inhibitory effects on nicotine‐stimulated tyrosine hydroxylase activity and adrenaline secretion. 6 A structurally related protein kinase C inhibitor, bisindolylmaleimide I, inhibited PDBu‐stimulated tyrosine hydroxylase activity with an IC 50 of < 1 μ m and complete inhibition by 3 μ m , but had essentially no effect on nicotine stimulated tyrosine hydroxylase activity or catecholamine secretion. 7 The results suggest that Ro 31–8220 is not only a protein kinase C inhibitor but is also a potent inhibitor of nicotinic receptor responses in adrenal chromaffin cells by a mechanism unrelated to protein kinase C inhibition. The results are consistent with Ro 31–8220 being a nicotinic receptor antagonist.