PREVALENCE OF IMPAIRED RESPONSIVENESS TO EPINEPHRINE IN PLATELETS AMONG JAPANESE

The responsiveness of platelets only to epinephrine was markedly impai red in 23/140 (16%) healthy Japanese. The impaired responsiveness was not altered by changes in time and environment. Circulating level of c atecholamines did not affect the responsiveness of platelets to epinep hrine. A pilot family study indicated a possible familial nature of th e defect. H-3 methyl yohimbine binding studies indicated that this def ect was due to the decreased number of alpha 2 adrenergic receptor. De spite the defect, the potentiating effect of epinephrine on platelet a ggregation stimulated by a low dose of ADP was normal. This abnormalit y is not apparently associated with any bleeding disorders and the cli nical implication is unknown at present. It is, however, essential to acknowledge the prevalence of such defect in pursuing research on plat elets stimulated by epinephrine.