Human platelet calcium measurements. Methodological considerations and comparisons with calcium mobilization in vascular smooth muscle cells.
Platelets are used as models for vascular smooth muscle cells (VSMC) in evaluating intracellular calcium ([Ca2+]i) metabolism in humans. This study was designed to determine if agonist-induced increases in [Ca2+]i in platelets occur via release from intracellular stores as previously demonstrated for VSMC. Incubation of purified platelets loaded with fura-2-AM in media containing 1.5 mmol/L Ca2+ resulted in higher basal [Ca2+]i than platelets incubated in Ca(2+)-free media. In addition, vasopressin-induced platelet [Ca2+]i transients were almost completely blocked by Ca2+ channel blockers. Thus, in contrast to VSMC, the transmembranous flux of extracellular Ca2+ is the major mechanism in vasopressin-induced increases in platelet [Ca2+]i, while mobilization of intracellular Ca2+ stores is only minimally involved.
Standley
P R
PR
Wayne State University School of Medicine, Detroit, Michigan 48201.
Gangasani
S
S
Prakash
R
R
Zemel
M B
MB
Sowers
J R
JR
D001127:Arginine Vasopressin / Q000494:pharmacology; D001792:Blood Platelets / Q000737:chemistry* / Q000378:metabolism; D002118:Calcium / Q000097:blood*; D016257:Fura-2 / Q000031:analogs & derivatives; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism
C049925:fura-2-am; D001127:Arginine Vasopressin; D002118:Calcium; D016257:Fura-2