title: Multihormonal regulation of progesterone synthesis in cultured human midluteal cells.
abstract: The objectives of this investigation were to examine in vivo insulin like-growth factor-I (IGF-I) secretion by the human midcorpora lutea (mid-CL) and the effects of IGF-I, hCG, FSH, and human GH on progesterone (P) production by CL cells obtained from patients at laparotomy. We first examined whether the CL produces IGF-I by measuring IGF-I levels in the ovarian vein from the ovary bearing the CL. The IGF-I concentration in the ovarian vein bearing the CL (206 +/- 31 ng/mL) was significantly increased compared to the concentration in the contralateral ovarian vein (179.2 +/- 32 ng/mL; P < 0.05). Luteal cells isolated from mid-CL were cultured in serum-free medium 199 in the presence and absence of hCG, FSH, GH, and graded concentrations of IGF-I. At the end of the incubation period (24 h), P levels in the medium were measured by RIA. The treatment with IGF-I (0.1-10 ng/mL) showed a dose-dependent stimulatory action of IGF-I on P synthesis in the luteal cell system, being maximal between 5-10 ng/mL. The treatment with hCG (10 IU/mL), IGF-I (5 ng/mL), and GH (1000 ng/mL) increased basal P synthesis by 300%, 80%, and 30%, respectively (P < 0.001 and P < 0.05). FSH (100 ng/mL), either alone or in combination with IGF-I, failed to stimulate P synthesis. Treatment with IGF-I monoclonal antibody (1:5000) completely reduced P synthesis induced by 5 ng/mL IGF-I and slightly reduced basal P synthesis as well as GH-stimulated P synthesis by human midluteal cells. To further evaluate the specific role of IGF-I on luteal steroidogenesis, IGF-I receptor was identified by chemical cross-linking of [125I]IGF-I to mid-CL membranes. Experiments conducted in the absence and presence of unlabeled IGF-I (500 ng) revealed proteins with characteristics of the type I IGF receptor. These results are consistent with multihormonal regulation of P synthesis by the human mid-CL. hCG and IGF-I play a major role in the stimulation of P synthesis and, to a lesser extent, human GH. These in vivo and in vitro data suggest that the CL is a site of secretion, action, and reception of IGF-I during the midluteal phase.
authors.affiliation: University of Chile School of Medicine, Santiago.
authors.forename: L
authors.initials: L
authors.lastname: Devoto
authors.forename: P
authors.initials: P
authors.lastname: Kohen
authors.forename: O
authors.initials: O
authors.lastname: Castro
authors.forename: M
authors.initials: M
authors.lastname: Vega
authors.forename: J L
authors.initials: JL
authors.lastname: Troncoso
authors.forename: E
authors.initials: E
authors.lastname: Charreau
mesh_terms: D000328:Adult; D000345:Affinity Labels; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006728:Hormones / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D008183:Luteal Phase; D010053:Ovary / Q000098:blood supply; D011374:Progesterone / Q000096:biosynthesis*; D014680:Veins
chemical_list: D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D006728:Hormones; D011374:Progesterone