EFFECTS OF AGE, SEX AND THE ORAL-CONTRACEPTIVE ON THE PLATELET MEMBRANE FIBRINOGEN BINDING-SITE (GLYCOPROTEIN-IIB GLYCOPROTEIN-IIIA)

1 We have studied the effects of age, sex and the oral contraceptive pill on platelet fibrinogen 'receptor' density (B(max)) and affinity (K(d)). 2 [I-125]-fibrinogen binding to gel-filtered platelets was assessed after stimulation with adenosine 5-diphosphate (ADP) and thrombin in 60 normal subjects; 37 females and 23 males. 3 For both agonists there was no significant difference in B(max) or K(d) between the sexes. A trend towards increasing affinity (reduced K(d) with age was noted in the female group following ADP stimulation. This was not considered to be physiologically relevant. In the group as a whole no significant relationship of B(max) and K(d) with age was demonstrated. 4 A further group of eight women taking low dose oestrogen combined oral contraceptive pill were studied on days 7, 14, 21 and 28 of the treatment cycle and compared with eight women with regular ovulatory cycles. No significant variations in B(max) or K(d) were detected within or between cycles in these two groups.