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Effects of Substance P on Carbachol‐Stimulated 45 Ca 2+ Uptake into Cultured Adrenal Chromaffin Cells
Author(s) -
Boksa P.
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.tb10549.x
Subject(s) - carbachol , substance p , chemistry , catecholamine , endocrinology , medicine , acetylcholine , extracellular , calcium , chromaffin cell , cholinergic , receptor , adrenal medulla , biochemistry , biology , neuropeptide , organic chemistry
Substance P is known to modulate acetylcholine‐induced catecholamine release from adrenal chromaffin cells. To investigate the mechanisms involved in this modulation, the present study examined the effects of substance P on net 45 Ca 2+ fluxes in cultures of bovine adrenal chromaffin cells. Two effects of substance P were observed: (1) Substance P inhibited carbachol‐induced 45 Ca 2+ uptake and 45 Ca 2+ efflux and (2) substance P protected against desensitization of carbachol‐induced 45 Ca 2+ uptake and 45 Ca 2+ efflux. Thus substance P modulates two other cholinergic responses, 45 Ca 2+ uptake and 45 Ca 2+ efflux, in a manner similar to its modulation of catecholamine release. The results also indicate that substance P's inhibition of net carbachol‐induced 45 Ca 2+ uptake is due to inhibition of 45 Ca 2+ uptake rather than enhancement of 45 Ca 2+ efflux. Substance P almost completely inhibited carbachol‐induced 45 Ca 2+ uptake in both Na + ‐containing and Na + ‐free media, suggesting that substance P can inhibit the uptake of 45 Ca 2+ induced by carbachol regardless of whether 45 Ca 2+ is taken up through voltage‐sensitive or acetylcholine receptor‐linked channels. However, substance P produced only a small inhibition of K + ‐induced 45 Ca 2+ uptake, indicating that substance P does not interact directly with voltage‐sensitive Ca 2+ channels. In addition, substance P's inhibition of carbachol‐induced 45 Ca 2+ uptake was noncompetitive with respect to Ca 2+ , and increasing concentrations of extracellular Ca 2+ were unable to overcome substance P's inhibition of [ 3 H]‐norepinephrine ([ 3 H]NE) release. It is concluded that substance P does not interact directly with Ca 2+ channels in bovine adrenal chromaffin cells.