Effect of the oxytocin antagonist antocin and agonist decomoton on baboon luteal cell production and release of progesterone

OBJECTIVE: To evaluate the effect of oxytocin, its antagonist antocin, and agonist decomoton on baboon luteal cell P secretion. DESIGN: Prospective study. SETTING: Academic department of obstetrics and gynecology in a US medical school. ANIMAL(S): Luteal-phased timed corpora lutea (CL) from a cohort of adult cycling baboons (Papio anubis). INTERVENTION(S): Dispersed luteal cells from luteal phase baboon CL were cultured and treated with nothing (control), oxytocin (4-400 mU), antocin (4-400 microg), oxytocin with antocin, decomoton (4-400 microg), or oxytocin with decomoton. MAIN OUTCOME MEASURE(S): Basal and hCG (10 U)-stimulated P were measured in the incubate. RESULT(S): Basal P secretion did not change significantly with all peptides studied. The hCG-stimulated P secretion was significantly inhibited by oxytocin (4-400 mU), antocin (4-400 microg), and antocin combined with oxytocin, and with oxytocin, decomoton, and decomoton combined with oxytocin. Antocin (-12%) was less inhibitory than oxytocin (-25% to -22%). Antocin combined with oxytocin enhanced the inhibition to -35% to -39%. Decomoton had stronger (not significant) inhibition than oxytocin. Mean inhibition was 28%-35% with all doses of oxytocin, decomoton, or combined together. CONCLUSION(S): Although decomoton, an oxytocin agonist inhibited hCG-stimulated luteal cell P secretion in vitro, antocin also acted like an agonist, rather than an antagonist, in inhibiting P secretion.