[Biochemical features of platelet alpha2-adrenergic receptors and their connection with an increase in concentration of intracellular Ca2+].
Epinephrine (E) and norepinephrine (NE) alone did not increase free intracellular Ca2+ ([Ca2+]i) in human platelets loaded with Quin-2 or Fura-2; however, they did potentiate the effects of vasopressin (VP), serotonin (S) and platelet activating factor (PAF). The synergism in [Ca2+]i increase was also obtained in the presence of VP together with PAF, S with PAF as well as VP with S. The effect of E or NE was blocked by yohimbine and phentolamine. Prazosin was less effective, while propranolol had no effect at all. Clonidine did not potentiate the effects of VP, S or PAF on [Ca2+]i; however, it did block the potentiation induced by E or NE. E potentiated the VP-induced 45Ca2+ uptake as well as VP-stimulated inositol 1,4,5-trisphosphate (IP3) formation. E alone did not change significantly the level of IP3 in platelets, nor did it influence the cyclic AMP level. The experimental results suggest that both Ca2+ influx and polyphosphoinositide breakdown underlie the mechanism of potentiation.
Negresku
E V
EV
Baldenkov
G N
GN
Grigorian
G Iu
GIu
Mazaev
A V
AV
Tkachuk
V A
VA
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D000242:Cyclic AMP / Q000378:metabolism; D003864:Depression, Chemical; D004837:Epinephrine / Q000378:metabolism; D006801:Humans; D009638:Norepinephrine / Q000378:metabolism; D010646:Phentolamine / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000378:metabolism; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism; D013268:Stimulation, Chemical; D014667:Vasopressins / Q000378:metabolism; D015016:Yohimbine / Q000494:pharmacology
D010972:Platelet Activating Factor; D011942:Receptors, Adrenergic, alpha; D014667:Vasopressins; D015016:Yohimbine; D012701:Serotonin; D011433:Propranolol; D000242:Cyclic AMP; D002118:Calcium; D009638:Norepinephrine; D011224:Prazosin; D004837:Epinephrine; D010646:Phentolamine
Biokhimicheskie osobennosti alpha2-adrenoretseptorov trombotsitov i ikh sviaz' s povysheniem kontsentratsii vnutrikletochnogo Ca2+.