HEPATIC LIPASE GENE-EXPRESSION IS TRANSIENTLY INDUCED BY GONADOTROPIC-HORMONES IN RAT OVARIES

Hepatic lipase (HL) gene expression was studied in rat ovaries. A tran script lacking exons 1 and 2 could be detected by reverse transcriptio n-polymerase chain reaction (RT-PCR) in the ovaries of mature cyclic f emales and of immature rats treated with pregnant mare serum followed by human chorionic gonadotropin (hCG) to induce superovulation. By com petitive RT-PCR the HL transcript was quantified. Low levels of HL mRN A were detected in ovaries of mature cyclic females and of immature ra ts. During superovulation HL mRNA was several fold higher than in matu re cyclic rats and transiently increased to a maximum at 2 days after hCG treatment. Pulse-labelling of ovarian cells and ovarian slices wit h [S-35]methionine followed by immunoprecipitation with polyclonal ant i-HL IgGs showed de novo synthesis of a 47 kDa HL-related protein. Exp ression of the protein was transiently induced by gonadotropins with a peak at 2 days after hCG treatment. Induction of liver-type lipase ac tivity occurred only after HL mRNA and synthesis of the HL-related pro tein had returned to pre-stimulatory levels. We conclude that in rat o varies the HL gene is expressed into a variant mRNA and a 47 kDa prote in. The expression of the HL gene in ovaries is inducible and precedes the expression of the mature, enzymatically active liver-type lipase. Copyright (C) 1997 Elsevier Science Ireland Ltd.