Effect of cyclic AMP on cytoplasmic free calcium in human platelets stimulated by thrombin: direct measurement with quin2.
With the fluorescent Ca2+ indicator quin2, we measured directly cytoplasmic free Ca2+ [( Ca2+]i) in washed human platelets stimulated by thrombin and examined the effect of cyclic AMP on [Ca2+]i levels and 14C-serotonin release. Thrombin (0.2 U/ml) evoked a rise in [Ca2+]i from the basal level of about 100 nM to integral of 3 microM which was fast enough to trigger serotonin release. This rise was inhibited in a dose-dependent manner by preincubation with prostaglandin E1 (PGE1) (0.1-10 microM) or dibutyryl cyclic AMP (0.01 -1 mM). Parallel to this, serotonin release was also inhibited by these drugs. When added to platelets after stimulation by thrombin, PGE1 caused the rapid decrease of elevated [Ca2+]i. These results provide direct evidence that [Ca2+]i levels in platelets are regulated by cyclic AMP.
D000634:Aminoquinolines; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D000242:Cyclic AMP / Q000097:blood*; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D012701:Serotonin / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism
D000634:Aminoquinolines; D012701:Serotonin; C035738:Quin2-acetoxymethyl ester; D000242:Cyclic AMP; D013917:Thrombin; D002118:Calcium