Membrane mechanism mediates progesterone stimulatory effect on LHRH release from superfused rat hypothalami in vitro.
To determine whether the plasma membrane is a primary site for progesterone (P4) action on the neural LHRH apparatus of hypothalamic tissues derived from ovariectomized, estradiol-primed (OVX + E2) immature rats, immobilized P4 was infused directly to these tissues using a superfusion technique. Two kinds of immobilized P4 with bovine serum albumin (BSA) conjugated at positions 3 or 11, or 11-deoxycorticosterone (DOC) immobilized at position 21 of the steroid molecule, respectively, were tested for structural specificity. Among the three immobilized steroids, only P4 with BSA conjugated at position 3 (P4-3-BSA) was effective in stimulating LHRH release in vitro. P4-3-BSA at 0.5 micrograms/ml, approximately 1.7 X 10(-7) M of P4, increased LHRH levels in the superfusates to about 2.5-fold those of pretreatment levels. In addition, no conversion of P4-3-BSA to free progesterone was detected. This observation demonstrated that the plasma membrane is a primary site for the stimulating effect of P4 on LHRH release from hypothalamic tissue in vitro.
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D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats
D004343:Drug Implants; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol