Heterogeneity of caffeine- and bradykinin-sensitive Ca2+ stores in vascular endothelial cells.
The filling state of Ca2+ stores in endothelial cells regulates Ca2+ entry. The functional relationship between the major Ca2+ stores [i.e. Ins(1,4,5)P3-sensitive (= bradykinin-sensitive stores, 'BsS') and caffeine-sensitive stores] is unknown. In pig right-coronary-artery endothelial cells, caffeine failed to release Ca2+ in 68% of the cells (quiet-responders), but increased bradykinin (Bk)-induced Ca2+ release 2.5-fold. In Bk-pre-stimulated cells, caffeine increased Ca2+ release upon a second stimulation with Bk 3.2-fold. In quiet-responders caffeine alone did not affect net Ca2+ storage, whereas Bk or caffeine followed by Bk decreased the intracellular Ca2+ pool to 45% and 15%, respectively. Blockade of the endoplasmic-reticulum Ca2+ pump by thapsigargin unmasked the effect of caffeine in quiet-responders, resulting in a transient increase in intracellular free Ca2+ concentration ([Ca2+]i). In 37% of the cells caffeine alone transiently increased [Ca2+]i and depleted BsS. This study suggests a heterogeneity in functional organization of endothelial Ca2+ stores. In quiet-responders, caffeine translocates Ca2+ towards the BsS, whereas in overt-responders caffeine empties the BsS.
Vascular Cell Biophysics Laboratory, Dalton Cardiovascular Research Center, University of Missouri, Columbia 65211.
W F
WF
Graier
S
S
Simecek
D K
DK
Bowles
M
M
Sturek
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002451:Cell Compartmentation; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D066298:In Vitro Techniques; D013552:Swine; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D013729:Terpenes; D002110:Caffeine; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D001920:Bradykinin; D002118:Calcium