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INVOLVEMENT OF PROTEIN KINASE C IN THE REGULATION OF Na + /Ca 2+ EXCHANGER IN BOVINE ADRENAL CHROMAFFIN CELLS
Author(s) -
Soma Shin,
Kuwashima Haruhiro,
Matsumura Chiaki,
Kimura Tomohiko
Publication year - 2009
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2009.05140.x
Subject(s) - chelerythrine , protein kinase c , veratridine , bisindolylmaleimide , catecholamine , chromaffin cell , chemistry , medicine , activator (genetics) , ouabain , endocrinology , sodium calcium exchanger , adrenal medulla , calcium , biophysics , biochemistry , sodium , biology , kinase , receptor , intracellular , sodium channel , organic chemistry
SUMMARY1 The Na + /Ca 2+ exchanger (NCX) exchanges Na+ and Ca 2+ bidirectionally through the forward mode (Ca 2+ extrusion) or the reverse mode (Ca 2+ influx). The present study was undertaken to clarify the role of protein kinase C (PKC) in the regulation of NCX in bovine adrenal chromaffin cells. The Na + ‐loaded cells were prepared by treatment with 100 µmol/L ouabain and 50 µmol/L veratridine. Incubation of Na + ‐loaded cells with Na + ‐free solution in the presence of the Ca 2+ channel blockers nicardipine (3 µmol/L) and ω‐conotoxin MVIIC (0.3 µmol/L) caused Ca 2+ uptake and catecholamine release. 2 The Na + ‐dependent Ca 2+ uptake and catecholamine release were inhibited by 2‐[4‐[(2,5‐difluorophenyl)methoxy]phenoxy]‐5‐ethoxyaniline (SEA0400; 1 µmol/L) and 2‐[2‐[4‐(4‐nitrobenzyloxy)phenyl]isothiourea (KB‐R7943; 10 µmol/L), both NCX inhibitors. These results indicate that the Na + ‐dependent responses are mostly due to activation of the NCX working in the reverse mode. 3 In addition, we examined the effects of PKC inhibitors and an activator on the NCX‐mediated Ca 2+ uptake and catecholamine release. Bisindolylmaleimide I (0.3–10 µmol/L) and chelerythrine (3–100 µmol/L), both PKC inhibitors, inhibited NCX‐mediated responses. In contrast, phorbol 12,13‐dibutyrate (0.1–10 µmol/L), a PKC activator, enhanced the responses. Bisindolylmaleimide I and chelerythrine, at effective concentrations for inhibition of Na + ‐dependent catecholamine release, had a little or no effect on high K + ‐induced catecholamine release in intact cells or on Ca 2+ ‐induced catecholamine release in β‐escin‐permeabilized cells. 4 These results suggest that PKC is involved in the activation of NCX in bovine adrenal chromaffin cells.