Baboon corpus luteum: the effect of melatonin on in vitro progesterone production.

OBJECTIVE

To determine the effect of melatonin on baboon corpus luteum (CL) cell progesterone (P) production.

DESIGN

Five baboon CL obtained during the midluteal phase by luteectomy were dissociated using collagenase, and incubations were performed (50,000 cells per plate) in quadruplicate for 3 hours at 37 degrees C with melatonin (0.001 to 1.0 ng/mL) (basal) or with melatonin and 10 IU of human chorionic gonadotropin (hCG) (hCG-stimulated). Total P was measured by a specific radioimmunoassay.

MAIN OUTCOME MEASURES

Progesterone concentrations measured in the presence and absence of melatonin and hCG.

RESULTS

Melatonin (0.01 to 1.0 ng/mL) inhibited basal P production in all the CL (41.8 +/- 9.9 ng P without melatonin compared with 32.2 +/- 2.0 ng P, 28.4 +/- 2.1 ng with 0.01 and 1.0 ng/mL melatonin, respectively). Human chorionic gonadotropin-stimulated P production was significantly inhibited with as little as 0.01 ng of melatonin (150.8 +/- 11.4 ng with 10 IU hCG versus 120.3 +/- 6.4 ng with 10 IU hCG and 1.0 ng melatonin). The degree of inhibition in the hCG-stimulated cells was greater than in the nonstimulated cells. Melatonin at a concentration of 0.001 ng/mL did not affect P production in both stimulated and nonstimulated cells. Serotonin in similar concentrations had no effect on luteal cell P production.

CONCLUSION

These findings indicate that melatonin exerts a suppressive effect on baboon dispersed luteal cell P production and thus may play a role in luteal function.