title: Human platelet alpha-adrenergic receptors and responses during pregnancy: no change except that with differing hematocrit.
abstract: The possibility that platelet aggregation is altered during pregnancy is controversial. We tested for alterations of alpha-adrenergic receptor-induced platelet function during pregnancy compared to that in the early phase of the menstrual cycle. We found no change in alpha-adrenergic receptor concentration or in affinity of the receptor for epinephrine. The potency and sensitivity of epinephrine to inhibit adenylate cyclase, a response mediated by alpha 2-adrenergic receptors, was not different in platelets from the two groups of subjects. The ability of epinephrine to potentiate aggregation by adenosine diphosphate was significantly increased during pregnancy; however, this was an artifact introduced by lower hematocrits during pregnancy that resulted in an increased citrate concentration in the preparations of platelet-rich plasma from these women. The difference was eliminated by normalization of citrate concentration. Thus effects of alpha-adrenergic receptors on platelet function are not different during pregnancy. It is mandatory to recognize artifactual effects of differing hematocrits on platelet aggregation studied in vitro.
authors.forename: J M
authors.initials: JM
authors.lastname: Roberts
authors.forename: V
authors.initials: V
authors.lastname: Lewis
authors.forename: N
authors.initials: N
authors.lastname: Mize
authors.forename: A
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: J
authors.initials: J
authors.lastname: Starr
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002951:Citrates / Q000097:blood; D019343:Citric Acid; D004088:Dihydroergotoxine / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006400:Hematocrit; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D015016:Yohimbine / Q000378:metabolism
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D000316:Adrenergic alpha-Agonists; D002951:Citrates; D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D019343:Citric Acid; D015016:Yohimbine; D000262:Adenylyl Cyclases; D004837:Epinephrine