Premium
Arachidonic Acid Release and Catecholamine Secretion from Digitonin‐Treated Chromaffin Cells: Effects of Micromolar Calcium, Phorbol Ester, and Protein Alkylating Agents
Author(s) -
Frye Roy A.,
Holz Ronald W.
Publication year - 1985
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 - 10.1111/j.1471-4159.1985.tb07140.x
Subject(s) - digitonin , arachidonic acid , exocytosis , catecholamine , chromaffin cell , secretion , chemistry , protein kinase c , phorbol , biochemistry , endocrinology , biology , medicine , adrenal medulla , enzyme
The relationship between catecholamine secretion and arachidonic acid release from digitonin‐treated chromaffin cells was investigated. Digitonin renders permeable the plasma membranes of bovine adrenal chromaffin cells to Ca 2+ , ATP, and proteins. Digitonin‐treated cells undergo exocytosis of catecholamine in response to micromolar Ca 2+ in the medium. The addition of micromolar Ca 2+ to digitonin‐treated chromaffin cells that had been prelabeled with [ 3 H]arachidonic acid caused a marked increase in the release of [ 3 H]arachidonic acid. The time course of [ 3 H]arachidonic acid release paralleled catecholamine secretion. Although [ 3 H]arachidonic acid release and exocytosis were both activated by free Ca 2+ in the micromolar range, the activation of [ 3 H]arachidonic acid release occurred at Ca 2+ concentrations slightly lower than those required to activate exocytosis. Pretreatment of the chromaffin cells with N ‐ethylmaleimide (NEM) or p ‐bromophenacyl bromide (BPB) resulted in dose‐dependent inhibition of 10 μ M Ca 2+ ‐stimulated [ 3 H]arachidonic acid release and exocytosis. The IC 50 of NEM for both [ 3 H]arachidonic acid release and exocytosis was 40 μ M. The IC 50 of BPB for both events was 25 μ M. High concentrations (5–20 m M ) of Mg 2+ caused inhibition of catecholamine secretion without altering [ 3 H]arachidonic acid release. A phorbol ester that activates protein kinase C, 12‐ O ‐tetradecanoylphorbol‐13‐acetate (TPA), caused enhancement of both [ 3 H]arachidonic acid release and exocytosis. The findings demonstrate that [ 3 H]arachidonic acid release is stimulated during catecholamine secretion from digitonin‐treated chromaffin cells and they are consistent with a role for phospholipase A 2 in exocytosis from chromaffin cells. Furthermore the data suggest that protein kinase C can modulate both arachidonic acid release and exocytosis.