In vitro effects of luteinizing hormone, progesterone and oestradiol-17β on leptin gene expression and leptin secretion by porcine luteal cells obtained in early pregnancy.

Leptin, the product of the ob gene, is involved in the control of ovarian functions. Leptin transcripts and OB proteins were localized in the porcine corpus luteum, but the regulatory mechanism of leptin mRNA expression and leptin secretion in porcine luteal cells remains unexplained. The aim of the present study was to: 1) determine level of leptin and long form of leptin receptor (OB-Rb) transcript/protein in dispersed porcine luteal cells on days 14-16 of pregnancy and 2) examine, in vitro, the effects of luteinizing hormone (LH), 17β-oestradiol (E₂) and progesterone (P₄) on leptin gene expression and leptin secretion by those cells. Isolated luteal cells were first precultured (48 hours) and then cultured in the presence or absence of luteinizing hormone (LH) (1; 10; 100 ng/ml), E₂ (0.02; 0.2; 2; 20 ng/ml) and P₄ (20; 100; 200 ng/ml) for 24 hours. Leptin and OB-Rb transcript/protein were detected in porcine luteal cells by real-time PCR and fluorescence immunocytochemistry (F-ICC), respectively. A higher level of leptin mRNA expressions in the cells was observed in the presence LH (10 ng/ml), E₂ (0.02 ng/ml) and P₄ (200 ng/ml). The results of an RIA assay revealed increased leptin secretion when the luteal cells were treated with E₂ (20 ng/ml) and P₄ (200 ng/ml). LH did not affect leptin release by those cells. We conclude: 1) that leptin and OB-Rb genes/proteins are expressed in porcine luteal cells and 2) there is a modulatory effect of: LH, E₂ and P₄ on leptin mRNA expression as well as E₂ and P₄ on leptin secretion by those cells obtained in early pregnancy.