Dual-phase response of bovine pulmonary artery endothelial cells to agonists which increase free cytoplasmic calcium concentration.
The regulation of free cytoplasmic calcium concentration ([Ca2+]i) was studied in bovine pulmonary artery endothelial cells (BPAEC). The cells were seeded on the inner surface of glass cuvettes, grown to confluency and loaded with INDO-1. Using a multiwavelength method for estimation of [Ca2+]i it was shown that in Ca2+ containing medium a rapid rise of [Ca2+]i occurs in response to bradykinin, ATP or thrombin followed by a much slower decrease in free cytoplasmic calcium. Binding of extracellular Ca2+ by EGTA lowered basal [Ca2+]i but had no effect on the rate of agonist-induced [Ca2+]i increase or its absolute amount. In contrast, the kinetics of [Ca2+]i decrease were entirely different. A rapid (less than 0.5 min) decrease in [Ca2+]i to the basal level was observed immediately after the maximum had been achieved. If excess Ca2+ was added to the medium after EGTA, a second [Ca2+]i rise in response to the agonists occurred. The decrease in [Ca2+]i after the second peak was several times slower than the decrease in Ca2+ free medium. It is concluded that Ca2+ entry from the external medium had no effect on the maximal increase in [Ca2+]i but provides a severalfold increase in the duration the endothelial cell responses to the agonists.
Department of Medicine, University of Miami School of Medicine, Florida 33101.
P V
PV
Avdonin
B A
BA
Hayes
Pozin EYa
E G
EG
Popov
Gavrilov IYu
V A
VA
Tkachuk
U S
US
Ryan
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D003593:Cytoplasm / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology
D000255:Adenosine Triphosphate; D013917:Thrombin; D001920:Bradykinin; D002118:Calcium