Direct effects of the prostaglandins E-2 and F-2 alpha on progesterone release by the corpus luteum of the marmoset monkey (Callithrix jacchus) studied by in vitro microdialysis

The effects of the prostaglandins (PG) E-2 and F-2 alpha On progesterone se cretion in luteal tissue (32 corpora lutea) explanted from the mid-luteal o vary of the marmoset monkey (n=13) were investigated using an in vitro micr odialysis system. Consecutive applications of 1, 10 and 100 mu g/ml PGE(2) resulted in a significant increase in secretion of progesterone at the maxi mum dose of 100 mu g/ml, which was shown to be the stimulatory dose in both long-period and 20-min pulse (time to collect one fraction) applications. The response varied individually between 1.4- and 3.4-fold above the baseli ne concentrations. Application of 500 mu g/ml PGF(2 alpha) led to similar h ormone responses. In contrast, lower doses of PGF(2 alpha) (0.5, 5 and 50 m u g/ml) resulted in significantly increased levels of secretion of progeste rone, to approximately 1.4-fold baseline values, only after the application was terminated (echo effect). Responses were less variable when a short pu lse of 20 min duration was applied, instead of long applications of 1-2 h. On the basis of the passage rates measured for tritiated PGF(2 alpha), tran sfer through the dialysis membrane was assumed to be in the range of 1% for both PGs. Ultrastructurally, luteal cells lying in a sheath of five to sev en cell layers around the dialysis tubing appeared intact and were intercon nected by gap junctions. Vesiculation of the smooth endoplasmic reticulum w as more prominent after PG treatment, indicating a stimulation of cellular synthesis/secretory activities that was in accordance with the stimulatory action of both PGs on progesterone release under these in vitro conditions.