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Protein kinase C activator inhibits voltage‐sensitive Ca 2+ channels and catecholamine secretion in adrenal chromaffin cells

1995; Wiley; Volume: 359; Issue: 2-3 Linguagem: Inglês

10.1016/0014-5793(95)00026-6

1873-3468

Cristina M. Sena, Ângelo R. Tomé, Rosa M. Santos, Luı́s M. Rosário,

Protein Kinase Regulation and GTPase Signaling

We have investigated the effects of the phorbol ester 12-myristate 13-acetate (PMA) on depolarization-evoked Ca2+ influx and catecholamine secretion in bovine adrenal chromaffin cells. PMA (100 nM) strongly inhibited K(+)-evoked [Ca2+]i transients and Mn2+ quenching of fura-2 fluorescence. In contrast, 4 alpha-phorbol 12,13-didecanoate, a phorbol ester inactive on protein kinase C (PKC), had no effect. Maximal PMA-mediated inhibition occurred at 5-10 min incubations and were variable from cell to cell, ranging from 25 to 65% of controls. The [Ca2+]i transients evoked by the L-type Ca2+ channel activator Bay K 8644 were strongly inhibited by 100 nM PMA. PMA (0.1-10 microM) inhibited K(+)-evoked adrenaline and noradrenaline release by 23-44%. The data indicate that phorbol ester-mediated activation of PKC inhibits voltage-sensitive Ca2+ channels in chromaffin cells, leading to a prominent depression of depolarization-evoked catecholamine secretion.