Corelease of dynorphin-like immunoreactivity, luteinizing hormone, and follicle-stimulating hormone from rat adenohypophysis in vitro.
Rat anterior pituitary quarters or acutely dispersed rat anterior pituitary cells were incubated in vitro, and the release of dynorphin A1-13-like immunoreactivity (Dyn A1-13-IR) into the incubation medium was studied. Addition of LHRH led to a concentration-dependent enhancement of the release of Dyn A1-13-IR with a maximum secretory rate which was about 4-fold higher than basal secretion. Dyn A1-13-IR was released by LHRH concomitantly with LH and FSH, and the concentration-response relationships as well as the time course were virtually identical. Gel filtration and HPLC revealed a single peak of Dyn A1-13-IR, with an apparent mol wt of about 6000. In addition to Dyn A1-13-IR, alpha-neo-endorphin-like immunoreactivity was released by LHRH. The LHRH-stimulated release of Dyn A1-13-IR was mimicked by the LHRH analog D-Ala6,des-Gly10-LHRH ethylamide and blocked in a competitive manner by the LHRH antagonist D-pGlu1,D-Phe2,D-Trp3,6-LHRH. Addition of TRH (5 microM), rat corticotropin-releasing factor (100 nM), arginine vasopressin (1 microM), or synthetic human pancreatic GH-releasing hormone (10 nM) produced no effect on Dyn A1-13-IR release. An extract of the rat medial basal hypothalamus stimulated the release of Dyn A1-13-IR and beta-endorphin-like immunoreactivity, and the former, but not the latter, effect was blocked by the LHRH antagonist D-pGlu1,D-Phe2,D-Trp3,6-LHRH. These results demonstrate that dynorphin-like material and other proenkephalin B-derived peptides are released concomitantly with LH and FSH from rat adenohypophysis in vitro upon activation of LHRH receptors. This may indicate that proenkephalin B-derived peptides coexist with LH and/or FSH in at least some gonadotrophs of the normal rat anterior pituitary gland.
Knepel
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Schwaninger
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Döhler
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D000818:Animals; D002478:Cells, Cultured; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004399:Dynorphins / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D011919:Rats, Inbred Strains
D007987:Gonadotropin-Releasing Hormone; D004399:Dynorphins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone