title: Baboon corpus luteum: autonomous pulsatile progesterone secretion and evidence for an intraluteal oscillator demonstrated by in vitro microretrodialysis.
abstract: Pulsatility of serum progesterone (P) is usually ascribed to stimulation of the corpus luteum (CL) by pulsatile release of pituitary LH. We investigated P secretion by the primate CL by performing microretrodialysis on 6 fresh CL obtained at laparotomy from baboons (Papio anubis) with well defined menstrual cycles. Individually microdialyzed for 24-26 h with Dulbecco's Modified Eagle's Medium and Ham's F-12 enriched with HEPES buffer in a perifusion chamber, the retrodialyzed fluid was collected every 10 min and measured for P, estradiol, and 17 alpha-hydroxyprogesterone by specific and sensitive RIAs. The chronodynamics of hormone secretion were analyzed for pulse detection by PC-Pulsar 3.0. All 6 CL (2 each from early, LH +1 to +5; mid, LH +6 to +10; and late luteal phases, LH +11 to +15) demonstrated pulsatile secretion of P in vitro, with distinct and detectable peaks over the 24-26 h studied. The CL secreted 23-27 pulses of P in 24 h in early luteal, 8-20 pulses in midluteal, and 6-19 pulses in late luteal phases. Peak lengths were 23.8 +/- 18.5 to 35.7 +/- 17.1 min. Four CL gave interpeak intervals of 46-55 min, whereas two gave intervals of 136-137 min. Analysis of distribution of pulses against different interpulse intervals in individual CL and all CL together revealed a bell-shaped distribution, with the largest number of pulses seen at an interpulse interval of 21-40 min. Because of the low concentrations of estradiol and 17 alpha-hydroxyprogesterone retrodialyzed, a similar analysis of these data was not possible. Histological examination of the tissue at the termination of the experiment using hematoxylin and eosin and localization of 3 beta-hydroxysteroid dehydrogenase activity indicates that the steroidogenic potential of the tissue is minimally affected, although some morphological changes do occur. Our findings suggest autonomous pulsatile P secretion by the primate CL, indicating local control by and the presence of an intraluteal oscillator or pulse generator for P secretion.
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Texas Medical School, Houston 77030.
authors.forename: F S
authors.initials: FS
authors.lastname: Khan-Dawood
authors.forename: A R
authors.initials: AR
authors.lastname: Gargiulo
authors.forename: M Y
authors.initials: MY
authors.lastname: Dawood
mesh_terms: D000818:Animals; D003338:Corpus Luteum / Q000033:anatomy & histology / Q000378:metabolism*; D046508:Culture Techniques; D005260:Female; D008183:Luteal Phase / Q000502:physiology; D017551:Microdialysis; D010215:Papio; D010507:Periodicity; D011374:Progesterone / Q000378:metabolism*
chemical_list: D011374:Progesterone