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Angiotensin II Receptors Are Coupled to ω‐Conotoxin‐Sensitive Calcium Influx in Bovine Adrenal Medullary Chromaffin Cells
Author(s) -
McMillian M. K.,
Tuominen R. K.,
Hudson P. M.,
Suh H. H.,
Hong J. S.
Publication year - 1992
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.1471-4159.1992.tb11340.x
Subject(s) - chemistry , medicine , endocrinology , angiotensin ii , receptor , bradykinin , stimulation , ionomycin , chromaffin cell , agonist , phospholipase c , fura 2 , adrenal medulla , catecholamine , biochemistry , biology , cytosol , enzyme
The contribution of an ω‐conotoxin GVIA (ωCgtx)‐sensitive Ca 2+ influx pathway to the effects of angiotensin II (AII) receptor activation was examined in bovine adrenal medullary (BAM) cells. Pretreatment of BAM cells with 10 –6 M ωCgtx blocked stimulation of exocytosis by the degradation‐resistant analogue, sarcosine 1 –angiotensin II (S 1 ‐AII). In contrast, ωCgtx had no effect on basal secretion, nor did it inhibit [ 3 H]norepinephrine and [ 32 P]ATP release in response to bradykinin, another phospholipase C‐linked receptor agonist. Similarly, ωCgtx pretreatment inhibited the stimulation of 45 Ca 2+ uptake by S 1 ‐AII, but did not affect the response to bradykinin. This selective inhibition did not appear to be due to blockade of AII receptors by ωCgtx, as the accumulation of 3 H‐labeled inositol phosphates in response to S 1 ‐AII was not inhibited. The peak S 1 ‐AII‐stimulated increase in the intracellular free Ca 2+ concentration (Ca i ) in fura 2‐loaded BAM cells also was not significantly reduced by ωCgtx (or by stimulating in nominally Ca 2+ ‐free buffer), indicating that this response is dependent on intracellular Ca 2+ pools. However, a small ωCgtx‐sensitive Ca i response was detected after depletion of intracellular Ca 2+ pools with ionomycin. This study shows that AII receptors, but not bradykinin receptors, are linked to an ωCgtx‐sensitive Ca 2+ influx pathway in BAM cells.