Effect of Specific Estrogens on Prostaglandin Synthesis in Aorta and Thrombocytes of Female Pigeons

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Abstract
An increase in thromboembolism and coronary complications was noted in women following long-term intake of oral contraceptive steroids. Because of the role of platelets in thrombosis and atherogenesis, it is important to determine whether changes in platelet reactivity and aggregation occur following the intake of oral contraceptive steroids. The effect of 2 major natural estrogens (estrone and 17.beta.-estradiol) on prostaglandin [PG] biosynthesis from [14C]arachidonic acid in thrombocytes and aorta of female pigeons was compared with that of a male sex hormone (testosterone). In the aorta, 17.beta.-estradiol stimulated the synthesis of 6-keto PGF1.alpha. and PGF2.alpha. but markedly reduced the synthesis of PGE2. Estrone, on the other hand, stimulated the synthesis of PGE2. Testosterone stimulated the synthesis of all PG in the aorta. In the thrombocytes, 17.beta.-estradiol decreased aggregatory response to arachidonic acid and synthesis of thromboxane [TX] B2. Estrone increased aggregatory response to arachidonic acid. Testosterone decreased the synthesis of TX B2. These studies documented markedly different effects of estrone and 17.beta.-estradiol on PG metabolism in aorta and thrombocytes of female pigeons. Testosterone when administered to female pigeons might cause favorable effects through decrease in plasma lipid levels and the synthesis of TX B2 in thrombocytes.