Role of ω-Conotoxin GVIA-Sensitive Ca2+ Entry in Angiotensin II-Stimulated [3H]Phorbol 12, 13-Dibutyrate Binding in Bovine Adrenal Medullary Cells |
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Authors: | Michael K McMillian Pearlie M Hudson Harold H Suh Hong Ye Raimo K Tuominen John S Hong |
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Institution: | Laboratory of Molecular and Integrative Neuroscience, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, North Carolina, U.S.A. |
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Abstract: | Abstract: The relative contributions of Ca2+ influx and intracellular Ca2+ mobilization were examined for angiotensin II-stimulated 3H]phorbol 12, 13-dibutyrate binding, which reflects the level of activated protein kinase C in bovine chromaffin cells. Angiotensin II receptors activate phospholipase C in chromaffin cells, leading to a shortlived mobilization of intracellular Ca2+. Angiotensin II-stimulated 3H]phorbol 12, 13-dibutyrate binding was largely blocked in Ca2+-free buffer and by pretreatment with the Ca2+-channel blocker ω-conotoxin GVIA. The 3H]phorbol 12, 13-dibutyrate binding response to Sar1]angiotensin II also appeared to be voltage sensitive, as no additivity was observed with the response to the depolarizing agent 4-aminopyridine (3 m M ). Threshold sensitivities of the extra-and intracellular Ca2+-mobilizing pathways to angiotensin II were similar, and all examined effects of angiotensin II in these cells were apparently mediated by losartan-sensitive (AT1-Iike) receptors. The dependence of angiotensin II-stimulated 3H]phorbol 12, 13-dibutyrate binding on extracellular Ca2+ entry, in contrast to stimulation by other phospholipase C-linked receptor agonists (bradykinin and methacholine), suggests that angiotensin II preferentially stimulates protein kinase C translocation to the plasma membrane, rather than to internal membranes, in bovine adrenal medullary cells. |
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Keywords: | Chromaffin Adrenal medulla Protein kinase C Angiotensin II Phorbol dibutyrate binding K+ channels ω-Conotoxin GVIA |
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