Abstract
A role for prostacyclin (PGI 2) as a mediator of estrogen-induced increases in uterine blood volume (UBV) was investigated by measuring uterine tissue levels of 6-keto-prostaglandin F 1α (6-keto-PGF 1α), and testing estrogen responses in rats pretreated with the PGI 2 synthesis inhibitor, tranylcypromine (TCP). Uterine 6-keto-PGF 1α content was determined by radio-immunoassay of tissue extracts purified through the use of high-performance liquid chromatography (HPLC). Estrogen treatment of castrate rats resulted in a significant increase of uterine 6-keto-PGF 1α as compared to saline treated controls (9.3 ng/uterine horn vs 6.7 ng/uterine horn, p=0.01). Pretreatment with TCP (20 mg/kg) markedly reduced the uterine content of 6-keto-PGF 1α (2.5 ng/uterine horn). The typical 50% increase in UBV observed after estrogen was unaffected by tranylcypromine pretreatment. It was concluded that the increased PGI 2 synthesis, as indicated by elevated levels of 6-keto-PGF 1α, may function as an amplifying mechanism for the uterine vasodilation-induced by estrogen in castrate rats, but that production of this prostanoid is not essential for the estrogen response.
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