Depolarization potentiates endothelin-induced effects on cytosolic calcium in bovine adrenal chromaffin cells.
The effects of endothelin on intracellular calcium concentrations ([Ca2+i]) in primary cultures of bovine adrenal chromaffin cells (BAM) were measured using Fura 2. Endothelin had minimal effects on [Ca2+i] over a broad dose range (1 nM to 1 microM). However, in conjunction with K+ depolarization there was a synergistic increase in [Ca2+i]. This effect was dependent on extracellular calcium as was the response to KCl alone. A partial synergistic effect was evident with endothelin and nicotinic stimulation. The effects of endothelin and angiotensin II on [Ca2+i] are only additive. Blockade of voltage sensitive calcium channels failed to alter the synergistic effects. Our results indicate that endothelin influences BAM calcium mobilization through sites regulated by membrane depolarization but differing from traditional voltage sensitive calcium channels.
Rasmussen
K
K
Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093.
Printz
M P
MP
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D016232:Endothelins; D004730:Endothelium, Vascular / Q000502:physiology; D016257:Fura-2; D007294:Inositol / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology
D001572:Benzofurans; D016232:Endothelins; D010455:Peptides; D010716:Phosphatidylinositols; D000804:Angiotensin II; D007294:Inositol; D011189:Potassium Chloride; D009538:Nicotine; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium; D016257:Fura-2; D009638:Norepinephrine