Extraction, isolation and identification of a luteolytic substance from bovine endometrium

Abstract

A series of experiments was conducted leading to the isolation and identification of arachidonic acid as a luteolytic agent in extracts of bovine endometrial tissue. Luteolytic activity was followed during fractionation of endometrial tissue by measuring corpus luteum weights and progesterone contents in the ovaries of pseudopregnant hysterectomized hamsters injected with each fraction. The luteolytic activity was removed from an active protein fraction and identified as a fatty acid. Fatty acids from the microsomal fraction of the endometrium were found to be particularly active. The luteolysin was identified as arachidonic acid by the following criteria: identical Rf's for the active material and arachidonic acid in several thin layer chromatography systems, identical retention times for methylated arachidonic acid and one component of the active substance on gas liquid chromatography (GLC), using three separate columns, and identical mass spectra for arachidonic acid and one component of the active material obtained by GLC. Sufficient arachidonic acid was present in the active fractions to produce the luteolytic effects observed. The effect of arachidonic acid is specific; no other similar fatty acids tested were luteolytic. Unsaturation seems essential for luteolytic activity, since hydrogenation of both arachidonic and the purified active endometrial fraction destroyed the activity. The role of arachidonic acid of uterine origin in luteolysis in the cow remains to be determined.