Ca2+ influx induced by the Ca(2+)-ATPase inhibitors 2,5-di-(t-butyl)-1,4-benzohydroquinone and thapsigargin in bovine adrenal chromaffin cells.
We have characterized the effect of the Ca(2+)-ATPase inhibitors 2,5-di-(t-butyl)-1,4-benzohydroquinone (tBHQ) and thapsigargin on the concentration of cytosolic Ca2+ in single bovine adrenal chromaffin cells by video-imaging of fura-2-loaded cells. Addition of either inhibitor released Ca2+ from internal stores in the absence of external Ca2+. tBHQ was unable to stimulate further Ca2+ release after addition of thapsigargin, but thapsigargin could do so after release by tBHQ, indicating that the tBHQ-sensitive stores are a sub-set of those sensitive to thapsigargin. Angiotensin II was able to elicit Ca2+ release after application of tBHQ, indicating that at least part of the tBHQ-sensitive stores were distinct from those discharged by Ins(1,4,5)P3. In the presence of external Ca2+, both Ca(2+)-ATPase inhibitors produced a more prolonged rise in cytosolic Ca2+ consistent with stimulated Ca2+ entry. The ability of the inhibitors to activate a Ca(2+)-entry pathway was confirmed by monitoring quenching of fura-2 after stimulated entry of the Ca2+ surrogate Mn2+. These findings indicate that bovine adrenal chromaffin cells possess a mechanism by which Ca2+ entry can be activated, following emptying of certain internal stores, independently of receptor occupation.
Robinson
I M
IM
Physiological Laboratory, University of Liverpool, U.K.
Cheek
T R
TR
Burgoyne
R D
RD
D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002417:Cattle; D002451:Cell Compartmentation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014741:Video Recording
D006873:Hydroquinones; D013729:Terpenes; D000804:Angiotensin II; D019284:Thapsigargin; C018855:2-tert-butylhydroquinone; D000252:Calcium-Transporting ATPases; D002118:Calcium