Concentrations and Activities of Prostaglandins of the F Series in Bovine Tissue, Blood, and Milk

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Abstract
Relatively effective methods for extracting PGF [prostaglandin F] from tissues and milk and for eliminating contaminating lipids from the extracts were developed. Concentrations of PGF rose in bovine endometrium and in uterine venous plasma at the 15th-17th day of the estrous cycle, coincident with or just prior to the onset of corpus luteum regression and decline in plasma progesterone concentrations. A selective transfer of PGF 2.alpha. from the utero-ovarian vein to the ovarian artery after placing a luteolytic dose into the lumen of the uterus can be demonstrated. That this mechanism operates in the normal cow could not be shown, since PGF concentrations in ovarian arterial blood remained low at all times during the estrous cycle, even when concentrations in uterine venous blood were high. Exogenous PGF2.alpha. increased peripheral plasma concentrations of estrone and estradiol. Increased plasma estrogen concentrations were demonstrated after PGF2.alpha. administration, even in the presence of plasma progesterone concentrations of 2-3 ng/ml. Increased synthesis of PGF2.alpha. and elevated plasma estrogen followed injections of arachidonic acid directly into the corpus luteum. Measurements of PGF in milk before and after exogenous administration of PGF2.alpha. indicate that low, and rather variable, concentrations are in milk of normal cows, and that these concentrations are not elevated significantly for more than about 7 h after administration of the compound. No evidence was found for elevated concentrations of testosterone in milk of PGF2.alpha. treated cows.

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