Leptin levels and leptin and its receptor expresion in pig placenta.

Leptin, an adipocyte hormone involved in energy homeostasis, plays a role in the control of reproduction and pregnancy. The objective of this study was to unravel a possible relationship between maternal plasma leptin concentrations and leptin receptor gene expression in swine. A total of 15 crossbred multiparous sows aging 24 - 36 months with an average weight of 160  10 kg were used. Blood samplings started 2 weeks before A.I. and were carried out every 15 dd until 45 dd of gestation; thereafter, blood samples were obtained weekly until 1 month post-partum. Leptin plasma levels were measured by the Linco Multi-Species Leptin Assay Kit; total RNA was extracted from placental tissue and RT-PCR was carried out with specific primers. Maternal leptin levels significantly (p<0.05) increased during the last third of gestation; they weren’t related with neither piglet number nor weight. Results of RT-PCR studies evidenced the expression of both leptin and receptor long (but not short) form; the long form had been predicted to be the predominantly functional receptor. The co-presence of hormone and receptor in the same organ implies a possible autocrine/paracrine effect. These results suggest that leptin may be involved in placental endocrine function.