Alteration of platelet responses to metabolites of arachidonic acid by oral contraceptives

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Abstract
The effects of oral contraceptive (OC) usage on platelet responsiveness to arachidonic acid metabolites was investigated. Platelets obtained from women who were taking oral contraceptives for at least 3 mo. were compared with those of age-matched controls. Both the basal and prostacyclin (PGI2)-stimulated platelet cAMP levels were significantly lower in OC users than in non-users. There was no significant difference in the PGD2[prostaglandin D-2]-stimulated cAMP levels between the 2 groups. Platelet aggregability to U46619, a TXA2 [thromboxane A-2] agonist, was greatly enhanced by OC. OC usage can specifically enhance platelet responsiveness to TXA2 while suppressing platelet responsiveness to PGI2. Their overall effect would be a disruption of normal platelet responses in favor of thrombus formation.