Interaction between anterior pituitary prodynorphin and the secretion of luteinizing hormone (LH).
The purpose of present research was to investigate the possible involvement of prodynorphin (proDYN)-derived peptides acting locally within the anterior pituitary (AP) on the effects of estradiol-17 beta (E2) and gonadotropin-releasing hormone (GnRH) on the release of luteinizing hormone (LH). Exposure of bovine AP cells in primary suspension cultures to E2 increased (P < 0.05) the spontaneous release of proDYN-derived peptides and also augmented (P < 0.05) the GnRH-induced release of LH. Both of these E2-induced responses required either high E2 dosages or prolonged exposure to produce significant changes, but there were a few cases in which the association between E2-induced changes in both parameters was absent. Therefore, it seems unlikely that proDYN-derived AP peptides mediate the effects of E2 on GnRH-induced LH release. Using another approach, cultured cells were exposed for 48 h to an antisense oligodeoxynucleotide (oligo) targeted against the translation initiation site of bovine proDYN. Compared with the two control treatments (scrambled oligo sequence or no oligo treatment), the antisense treatment decreased (P < 0.05) the quantity of LH released in response to challenge of the cells with 5 nM GnRH. There were no concurrent changes in cellular contents of proDYN-derived peptides or mRNA for LH-beta, but the antisense treatment tended to decrease (P < 0.10) the relative abundance of proDYN mRNA. In summary, proDYN-derived peptides probably do not mediate direct intrapituitary effects of E2 on LH, but the antisense treatment interfered in an unknown way with GnRH-induced release of LH from cultured AP cells.
D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004745:Enkephalins / Q000378:metabolism* / Q000502:physiology*; D004958:Estradiol / Q000494:pharmacology; D005300:Fertility Agents, Female / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D016376:Oligonucleotides, Antisense; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism* / Q000502:physiology*; D012313:RNA / Q000378:metabolism; D011863:Radioimmunoassay; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors