Role of luteal prostaglandins in the control of bovine corpus luteum functions.

Current and emerging concepts on regulation of bovine corpus luteum function by various metabolites of arachidonic acid are reviewed. A series of experiments are presented which support the concept that prostacyclin (PGI2), a metabolite of arachidonic acid via the cyclooxygenase pathway, plays a luteotropic role, and that products of the lipoxygenase pathway of arachidonic acid metabolism, particularly 5-hydroxyeicosatetraenoic acid (5-HETE), play a luteolytic role in the function of the bovine corpus luteum (CL). These ideas are supported by the following findings: injection of PGI2 directly into CL at mid-cycle produced a prolonged increase in peripheral plasma concentrations of progesterone; PGI2 stimulated synthesis of progesterone by dispersed luteal cells; synthesis of PGI2 by luteal cells was greatest during the period of early CL development (d 5 and 10), and diminished as the CL aged unless pregnancy ensued, causing a maintenance of the CL and synthesis of PGI2; administration of indomethacin, a blocker of synthesis of prostaglandin by the cyclooxygenase pathway, twice daily on d 4 to 6 of the estrous cycle inhibited CL development and caused a reduction in cycle length, suggesting the presence of a luteotropic prostaglandin; oxytocin administration twice daily on d 4 through 6 inhibited CL development and was accompanied by a 50% reduction in luteal synthesis of PGI2 by CL collected on d 7; large quantities of 5-HETE were found in luteal tissue; the addition of 5-HETE to dispersed luteal cells inhibited synthesis of progesterone and PGI2, while production of PGF2 alpha was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)