Abstract
The aim of this study is to investigate the effect of β-endorphin on cAMP and progesterone accumulation in rat luteal cells. Luteal cells of 4-day-old corpora lutea were cultured for 3h in the absence or presence of 0.001 or 0.01IU/ml hCG, and cAMP, progesterone and β-endorphin levels in the medium were measured by RIA. hCG stimulated the production of cAMP, progesterone and β-endorphin. In the presence of hCG, treatment with islet-activating protein (IAP) led to overall augmentation of cAMP and progesterone accumulation in comparison with untreated controls. In the absence or presence of low doses of hCG (0.001IU/ml), β-endorphin did not affect progesterone production, but inhibited cAMP accumulation. This inhibitory effect was abolished by pre-treatment with TAP. In the presence of high doses of hCG (0.01IU/ml), however, β-endorphin stimulated progesterone production without a corresponding increase in cAMP. This stimulatory effect was also abolished by IAP-treatment. These results suggest that luteal cells produce and release β-endorphin that affects cAMP and progesterone production via IAP-sensitive mechanisms.
