Serum Leptin Concentrations and Expression of Leptin Transcripts in Placental Trophoblast with Advancing Baboon Pregnancy

Leptin is a polypeptide hormone originally thought to be produced exclusively by adipocytes. Recently, however, both leptin messenger ribonucleic acid (mRNA) and leptin protein were identified in human placental trophoblast cells, suggesting a potential role in primate pregnancy. In the present study, venous blood samples were collected at 5-day intervals during gestation from baboons (Papio sp), an established model for the study of human pregnancy, as well as from nonpregnant baboons, and leptin concentrations were determined by RIA. Additionally, placental villous tissue was collected upon cesarean delivery at early (days 60–62; n = 5), mid (days 98–102; n= 5), and late (days 159–167; n = 5) gestation (term = ∼184 days), and leptin mRNA was quantitated by competitive RT-PCR. Finally, in situ hybridization was employed to localize transcripts to specific placental cell types. Results determined that maternal leptin levels (mean ± sem), which were dramatically greater (P < 0.01) than those in nonpregnant...