Direct in vitro effect of LH and steroids on leptin gene expression and leptin secretion by porcine luteal cells during the mid-luteal phase of the estrous cycle

Leptin, the product of the ob gene, is implicated in the control of reproductive functions in different species. Leptin transcript and protein are present in several tissues including adipose tissue and corpus luteum. The regulation of leptin mRNA expression and leptin secretion in porcine luteal cells is not clear. In this study, we determined leptin and OB-Rb mRNA/protein levels in porcine luteal cells during the mid-luteal phase of the estrous cycle (days 10–12) and examined, in vitro, the effects of LH, 17-β estradiol (E2) and progesterone (P4) on leptin gene expression and leptin secretion in those cells. Leptin and long form of leptin receptor (OB-Rb) mRNA expressions as well as leptin and OB-Rb protein were detected in the luteal cells by real-time PCR and fluorescence immunocytochemistry (F-ICC), respectively. Isolated luteal cells, after preliminary culture (48 h) were treated with LH (1; 10; 100 ng/ml), E2 (0.02; 0.2; 2; 20 ng/ml) and P4 (20; 100; 200 ng/ml) for 24 h. LH did not induce significant changes in leptin mRNA expression in the luteal cells. A higher level of leptin transcript was found in the presence of E2 (0.02 ng/ml) or P4 (200 ng/ml). Estradiol (0.2 ng/ml) and P4 (200 ng/ml) increased leptin secretion by luteal cells. Our results indicate that leptin and OB-Rb genes and proteins are expressed in porcine luteal cells and suggest that steroid hormones (E2 and P4) affect leptin mRNA expression and leptin secretion during the mid-luteal phase of the estrous cycle.