Baboon corpus luteum: size and sex steroid secretion throughout the luteal phase.

Objective: To determine the size of the baboon corpus luteum (CL) and levels of plasma P, 17alpha-hydroxyprogesterone (17-OHP), and E2 in the ovarian vein draining it, the contralateral ovarian vein, and peripheral blood throughout the luteal phase of the menstrual cycle.

Design: Prospective study.

Setting: Academic department of obstetrics and gynecology in a US medical school.

Animal(s): Corpora lutea from a cohort of 27 adult cycling baboons (Papio anubis).

Intervention(s): Timed luteectomy.

Main Outcome Measure(s): The authors weighed 166 CL and measured plasma P, 17-OHP, and E(2) in the blood samples obtained at luteectomy.

Result(s): Early luteal phase corpora lutea weighed 189.1 +/- 12.3 mg (mean +/- SEM); their weight significantly increased to 239.4 +/- 8.4 mg at mid luteal phase and significantly declined to 188.3 +/- 14.0 mg in late luteal phase. Plasma P draining the CL (134.4 +/- 20.5 ng/mL in early, 167.4 +/- 18.7 ng/mL in mid, and 126.4 +/- 23.4 ng/mL in late luteal phase) was significantly higher than that in contralateral ovarian (11.0 +/- 1.4 ng/mL) and peripheral plasma (7.1 +/- 0.9 ng/mL). Similarly, levels of both plasma 17-OHP (10.9 +/- 1.5 to 15.9 +/- 2.4 ng/mL) and E2 (1.6 +/- 0.2 to 2.6 +/- 0.6 ng/mL) draining the CL were significantly higher than those from the contralateral ovary and peripheral blood (17-OHP, 1.1 +/- 0.2 ng/mL; E2, 0.2 +/- 0.05 ng/mL).

Conclusion(s): Largest in mid luteal phase, the baboon CL secretes P, 17-OHP, and E2 throughout the luteal phase, with the highest levels seen in the ovarian vein draining the CL in the mid compared with the early and late luteal phases.