title: Granulosa layer: primary site of regulation of plasminogen activator messenger ribonucleic acid by luteinizing hormone in the avian ovary.
abstract: Plasminogen activator (PA) is hypothesized to be important in the remodeling of the extracellular matrix during follicular growth. The granulosa layer produces high amounts of PA in response to a stimulatory factor, produced by the theca layer, that is inhibited by LH. To determine the site and mechanism by which LH inhibits PA production, we asked 1) whether LH acts on the granulosa layer and/or the theca layer to inhibit PA production by the largest preovulatory follicle (F1), and 2) whether LH affects PA production by acting at the mRNA or protein level. Sections (10 mm in diameter) of granulosa layers obtained from the F1 follicle before (14 h before ovulation) or after (2 h before ovulation) the LH surge were incubated (24 h at 37 degrees C) in theca-conditioned medium; this medium had been prepared by incubation of 10-mm-diameter sections of theca layers, obtained before (14 h before ovulation) or after (2 h before ovulation) the LH surge, in Dulbecco's Modified Eagle's Medium for 24 h at 37 degrees C. PA production in culture medium was measured with use of the chromogenic substrate S-2251. PA production was high when granulosa layers obtained before the LH surge were incubated in theca-conditioned medium obtained before the LH surge; it was also high when granulosa layers obtained before the LH surge were incubated in theca-conditioned medium obtained after the LH surge. PA production was low when granulosa layers obtained after the LH surge were incubated in theca-conditioned medium obtained before the LH surge, and was also low when granulosa layers obtained after the LH surge were incubated in theca-conditioned medium obtained after the LH surge. Northern and Western blots and activity assays performed on granulosa layer homogenates indicated that PA mRNA, protein, and activity were high before the LH surge and low after the LH surge. Production of the stimulatory factor by the theca layer is apparently unaffected by LH. After exposure to LH, the granulosa layer is no longer capable of producing PA, even in the presence of the theca-derived stimulatory factor. We conclude that the granulosa layer is the site of mRNA and/or protein regulation of PA production by LH.
authors.affiliation: Department of Animal Sciences, University of Illinois at Urbana-Champaign 61801, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Tischkau
authors.forename: J A
authors.initials: JA
authors.lastname: Jackson
authors.forename: C
authors.initials: C
authors.lastname: Finnigan-Bunick
authors.forename: J M
authors.initials: JM
authors.lastname: Bahr
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002645:Chickens; D017077:Culture Media, Conditioned; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006107:Granulosa Cells / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D010960:Plasminogen Activators / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D013799:Theca Cells / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000096:biosynthesis / Q000235:genetics
chemical_list: D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D007986:Luteinizing Hormone; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator