Prolactin and testicular Leydig cell function: characterization of prolactin receptors in the murine MA-10 testicular Leydig cell line.
The direct role of prolactin (PRL) in testicular function is still unclear, mostly because of lack of a suitable in vitro model. To establish the suitability of the MA-10 murine tumor Leydig cell line for the study of PRL receptors (PRLR) and effects on steroidogenesis, we initially characterized PRLR on cultured MA-10 cells. The specific binding (Bs) of [125I]human growth hormone (hGH) depends on time, temperature, and Mg2+ ion and protein concentrations, with absolute specificity for the lactogenic hormones hGH and ovine PRL. Bs is saturable and is to a single class of high-affinity (Ka = 3.6 x 10(9) M-1) low-capacity (Bmax = 19.5 fmol/mg protein) binding sites. The molecular weight of PRLR, determined by cross-linking to [125I]hGH, SDS-PAGE and autoradiography, is 35 kDa for the free receptor, suggesting that the short-form PRLR protein, previously described in liver and mammary glands, is that primarily found in MA-10 cells. Thus, the demonstration of specific PRL binding sites on MA-10 Leydig cells, with characteristics similar to primary Leydig cell PRLR, suggests that this cell line can serve as a good model for both the study of PRLR mechanism of action and the role of PRL in Leydig cell function.
Department of Pharmacology, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
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Barkey
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Weiss-Messer
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Hacham
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Herscovich
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Ber
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Amit
D000818:Animals; D001665:Binding Sites; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D007984:Leydig Cell Tumor; D007985:Leydig Cells / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D008970:Molecular Weight; D011388:Prolactin / Q000494:pharmacology / Q000502:physiology*; D011981:Receptors, Prolactin / Q000737:chemistry / Q000502:physiology*; D014407:Tumor Cells, Cultured
D011981:Receptors, Prolactin; D011388:Prolactin; D013006:Growth Hormone; D008274:Magnesium