Prostaglandin Stimulation ofin VitroProgesterone Synthesis

Abstract

Bovine corpora lutea slices were incubated with prostaglandins and gonadotropins. All the prostaglandins tested (PGE 2 , PGE X , PGFjo and PGAi) were found to be steroidogenic, stimulating both the production of progesterone as measured in micrograms and the incorporation of radioactivity from acetate-l-u C. Prostaglandin E2 (PGE 2 ) gave the greatest effect, being approximately half as effective as luteinizing hormone (LH) on a molar basis. There were similarities between gonadotropin and prostaglandin. Cycloheximide (1 HIM) equally blocked the steroidogenic response to both PGE 2 and LH, the specific activities of the progesterone formed in the presence of prostaglandins and that formed in the presence of gonadotropins were approximately of the same order of magnitude, the time-response curves of PGE 2 and LH were similar, and there was no additive effect when prostaglandins were added to luteal slices incubated with saturating doses of either LH or human chorionic gonadotropin (HCG). These results are in contrast to the in vivo luteolytic effect of PGF 2 Q , and it is unlikely, therefore, that the luteolytic effect of PGF 2a is due to a direct inhibition of luteal steroidogenesis. Thus, the in vitro and in vivo effects of prostaglandins may represent 2 different mechanisms of action. (J Clin Endocr 30: 345, 1970)

Luteal blood flow and concentrations of circulating progesterone and other hormones associated with a simulated pulse of 13,14-dihydro-15-keto-prostaglandin F2α in heifers

“…The reason for the immediate positive progesterone response to PGF treatment is not known. Based on an in vitro study (Speroff & Ramwell 1970), a direct PGF steroidogenic stimulation of luteal cells has been suggested (Hixon & Hansel 1974). Direct inhibitory and stimulating effects of PGF on small and large luteal cells respectively have been demonstrated in vitro (Alila et al 1988, Meidan et al 1992, Girsh et al 1995, Okuda et al 1998, Skarzynski & Okuda 1999.…”

Effects of Intra-ovarian Bursal Injection of Eicosanoid Synthesis Inhibitors on Luteal Function in Immature Pseudopregnant Rats

“…Taken together, the increase or persistence in prostanoid biosynthesis in the late luteal phase is thought to be an important process in initiation of luteolysis. While both PGE 2 and PGI 2 are supposed to be luteotropic in vitro [16], the overall effects of prostanoids during the late luteal phase would be luteolytic. The mechanism by which NDGA affects luteal activity seems to be complex.…”

Interrelationships between progesterone, 13,14-dihydro-15-keto PGF-2a (PGFM) and LH in cyclic and early pregnant cows

“…It was also concluded from other studies of early (Little et ai, 1982;Roche et ai, 1985) and later (Schallenberger et ai, 1985a;Procknor et ai, 1986) (1985), and PGE-2 (Shemesh et ai, 1979;Shelton et ai, 1990). PGE-2 stimulates progesterone synthesis in dispersed bovine (Speroff & Ramwell, 1970) and ovine (Fitz et ai, 1984) luteal cells in vitro, although its action in vivo is not as clearly defined. Some in-vitro studies have also reported antagonism by PGE-2 of LH-stimulated progesterone synthesis in vitro (Thomas et ai, 1978;Stouffer et ai, 1979;Shelton et ai, 1990).…”