Inhibition of cyclic AMP accumulation in intact NCB-20 cells as a direct result of elevation of cytosolic Ca2+.
Earlier studies established that adenylyl cyclase in NCB-20 cell plasma membranes is inhibited by concentrations of Ca2+ that are achieved in intact cells. The present studies were undertaken to prove that agents such as bradykinin and ATP, which elevate the cytosolic Ca2+ concentration ([Ca2+]i) from internal stores in NCB-20 cells, could inhibit cyclic AMP (cAMP) accumulation as a result of their mobilization of [Ca2+]i and not by other mechanisms. Both bradykinin and ATP transiently inhibited [3H]cAMP accumulation in parallel with their transient mobilization of [Ca2+]i. The [Ca2+]i rise stimulated by bradykinin could be blocked by treatment with thapsigargin; this thapsigargin treatment precluded the inhibition of cAMP accumulation mediated by bradykinin (and ATP). A rapid rise in [Ca2+]i, as elicited by bradykinin, rather than the slow rise evoked by thapsigargin was required for inhibition of [3H]cAMP accumulation. Desensitization of protein kinase C did not modify the inhibitory action of bradykinin on [3H]cAMP. Effects of Ca2+ on phosphodiesterase were also excluded in the present studies. The accumulated data are consistent with the hypothesis that hormonal mobilization of [Ca2+]i leads directly to the inhibition of cAMP accumulation in these cells and presumably in other cells that express the Ca(2+)-inhibitable form of adenylyl cyclase.
Garritsen
A
A
Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262.
Zhang
Y
Y
Firestone
J A
JA
Browning
M D
MD
Cooper
D M
DM
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000037:antagonists & inhibitors*; D003600:Cytosol / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D010727:Phosphoric Diester Hydrolases / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014407:Tumor Cells, Cultured
D013729:Terpenes; D019284:Thapsigargin; D000242:Cyclic AMP; D011493:Protein Kinase C; D010727:Phosphoric Diester Hydrolases; D001920:Bradykinin; D002118:Calcium