Epinephrine sensitizes human platelets in vivo and in vitro as studied by fibrinogen binding and P-selectin expression.
Epinephrine (Epi) infusion influences platelet activation markers in vivo, but in vitro studies have mainly examined supraphysiological Epi concentrations and have yielded conflicting results. In this study whole-blood flow-cytometric measurements of platelet fibrinogen binding and P-selectin expression were used to compare enhancement of ADP (0.1 to 10 mumol/L)-induced platelet activation by Epi infusion in vivo (0.1 and 0.4 nmol.kg-1.min-1) and by Epi in vitro (10 and 50 nmol/L) in nine healthy volunteers. ADP caused concentration-dependent increases in the percentage of platelets that bound fibrinogen (from 4.4 +/- 0.9% to 69.9 +/- 4.2%) and that expressed P-selectin (from 4.5 +/- 0.5% to 44.2 +/- 3.8%). Fibrinogen and P-selectin binding indices (FgBI and PSBI; calculated from mean fluorescence intensity and percentage of positive cells) also increased from 0.18 +/- 0.03 to 11.70 +/- 1.99 for FgBI and from 0.22 +/- 0.03 to 2.34 +/- 0.29 for PSBI. Epi concentration-dependently enhanced fibrinogen binding and P-selectin expression in vitro (by approximately 30% at the midportion of the ADP curve at 10 nmol/L Epi; P < .001 for both by ANOVAs). High-dose Epi infusion enhanced FgBI similarly and increased maximal P-selectin expression by 38%. Epi (50 nmol/L in vitro) enhanced platelet activation further, whether samples were taken with or without prior Epi infusion. Total expression of glycoprotein IIb/IIIa was unaffected by Epi infusion, but glycoprotein Ib expression per platelet was reduced (P < .05). These in vivo and in vitro effects of Epi on platelet responses to agonist stimulation indicate a prothrombotic potential for sympathoadrenal activation in humans.
Hjemdahl
P
P
Department of Clinical Pharmacology, Karolinska Hospital, Stockholm, Sweden.
Chronos
N A
NA
Wilson
D J
DJ
Bouloux
P
P
Goodall
A H
AH
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000328:Adult; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D019007:P-Selectin; D015539:Platelet Activation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000097:blood* / Q000378:metabolism
D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D002118:Calcium; D004837:Epinephrine