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Studies on the Effect of Insulin‐Like Growth Factor‐I on Catecholamine Secretion from Chromaffin Cells
Author(s) -
Dahmer Mary K.,
Hart P. Michelle,
Perlman Robert L.
Publication year - 1990
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.1471-4159.1990.tb02340.x
Subject(s) - catecholamine , endocrinology , secretion , medicine , extracellular , chromaffin cell , biology , stimulation , chemistry , adrenal medulla , microbiology and biotechnology
Chromaffin cells cultured in serum‐free medium secreted a smaller percentage of their catecholamine stores in response to stimulation by high K + (55 m M ) than did cells cultured in serum‐containing medium. Addition of insulin‐like growth factor‐I (IGF‐I) to serum‐free medium restored high K + ‐stimulated catecholamine secretion to the levels seen in serum‐treated cultures. In contrast, addition of IGF‐I to serum‐containing medium had little effect on catecholamine secretion. These results suggest that serum contains IGF‐I or another factor that maintains the secretory responsiveness of chromaffin cells. IGF‐I not only enhanced high K + ‐stimulated catecholamine secretion, but also augmented secretion elicited by the nicotinic agonist dimethyl‐phenylpiperazinium, the dihydropyridine agonist Bay K 8644, and Ba 2+ . IGF‐I did not affect the dependence of catecholamine secretion on extracellular Ca 2+ concentration nor did it affect the time course of secretion. Experiments using 45 Ca 2+ demonstrated that IGF‐I treatment enhanced Ca 2+ uptake into the cells. When cells were permeabilized by treatment with digitonin, Ca 2+ ‐dependent catecholamine secretion was slightly, but consistently, greater from IGF‐I‐treated cells than from untreated cells. Our results suggest that IGF‐I may enhance catecholamine secretion partly by increasing Ca 2+ entry into the cells and partly by affecting a step distal to Ca 2+ entry.