In vitro microdialysis of baboon corpus luteum: effects of oxytocin on total and pulsatile progesterone secretion.
Baboon corpora lutea (two each from the early, mid- and late luteal phases) were individually microretrodialyzed in vitro for 48 h, 12 h initial baseline, 12 h retrodialysis with OT (9 mU/h), 12 h without OT and 12 h with cAMP (5 mmol/h). Progesterone (P) was measured by a sensitive and specific radioimmunoassay in 10-min fractions of retrodialysates and analyzed for P peaks by PC-pulsar 3.0. Neither OT nor cAMP had any effect on the characteristics of P pulses. In early and late luteal phase CL, OT inhibited P secretion within 1 h of administration followed by increased P secretion late during OT perfusion. In midluteal phase, OT did not affect P secretion. In all CL, P secretion was sustained or further increased during the 12 h after stopping OT. cAMP also sustained baseline or stimulated P secretion. In contrast, OT either increased total P output/12 h (28 to 49% above baseline) with a further increase of 21% to 296% above baseline after stopping OT, or inhibited total P output by 4% to 13% percent with a further decline of 51% to 61% after stopping OT. Thus, while overall OT is luteotropic, its dual effect (initial inhibition followed by stimulation) suggests direct and indirect effects through paracrine-autocrine mechanisms.
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Medical School at Houston 77030, USA.
F S
FS
Khan-Dawood
R
R
Chellaram
M Y
MY
Dawood
D000818:Animals; D003338:Corpus Luteum / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D005260:Female; D017551:Microdialysis; D010121:Oxytocin / Q000494:pharmacology*; D010215:Papio; D011374:Progesterone / Q000378:metabolism*
D011374:Progesterone; D010121:Oxytocin; D000242:Cyclic AMP