Effects of ATP and bradykinin on endothelial cell Ca2+ homeostasis and formation of cGMP and prostacyclin.
ATP and bradykinin are known to activate Ca2+ release from intracellular Ca2+ pools as well as induce the influx of Ca2+ in many cell types. In adrenal medulla endothelial cells, we found that ATP and bradykinin could activate Ca2+ influx, although Ca2+ influx did not appear to be due to depletion of intracellular Ca2+ pools per se, since depletion of intracellular Ca2+ pools with thapsigargin reduced rather than enhanced both unidirectional and steady-state 45Ca2+ uptake. In addition, Ca2+ influx, activated by ATP but not bradykinin, was mostly abolished after agonist removal in cells in which intracellular Ca2+ pools had not been allowed to refill, suggesting that continued receptor occupancy was necessary for ATP to activate Ca2+ influx. The role of Ca2+ in activating guanosine 3',5'-cyclic monophosphate (cGMP) formation [a marker for nitric oxide (NO) secretion] and prostacyclin (PGI2) secretion was also studied. Bradykinin-induced cGMP and PGI2 formation and ATP-induced PGI2 formation each required Ca2+ release from intracellular Ca2+ pools, since depletion of these pools with thapsigargin inhibited their formation. In contrast, ATP-induced cGMP formation, particularly at early time points, did not appear to require either Ca2+ release or Ca2+ influx. This suggests that ATP, but not bradykinin, either induces Ca(2+)-independent NO formation or that ATP stimulates the generation of cGMP independently of NO. The latter supposition is supported by our observation that NO synthase inhibitors inhibited ATP-induced cGMP formation by at most 50%.
Gosink
E C
EC
Department of Physiology, University of Wisconsin, Madison 53706.
Forsberg
E J
EJ
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000313:Adrenal Medulla / Q000098:blood supply; D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism*; D016257:Fura-2; D007295:Inositol Phosphates / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D008833:Microcirculation; D013552:Swine; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors
D007295:Inositol Phosphates; D013729:Terpenes; D004533:Egtazic Acid; D015759:Ionomycin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D011464:Epoprostenol; D001081:Apyrase; D000252:Calcium-Transporting ATPases; D006152:Cyclic GMP; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2