MOUSE PLACENTAL CELLS SECRETE SOLUBLE LEPTIN RECEPTOR (SOB-R) - CAMP INHIBITS SOB-R PRODUCTION

The aims of this study were to identify whether mouse placenta secrete s soluble OB-R (sOB-R) and to find the regulating factor of OB-R expre ssion. Total RNAs were extracted from placenta and decidua, and OB-R e xpression was assessed by Northern blot analysis. Decidua did not expr ess OB-R mRNA. However, OB-R mRNA expression was detectable in the pla centa on day 13 of pregnancy, and then it increased and reached a peak on day 17 of pregnancy. Mouse placental cells from day 12 of pregnanc y were cultured and OB-R gene expression was assessed by Northern blot analysis. OB-R mRNA expression was detectable from the second day of culture and reached a peak on the third day of culture. To determine w hether placental cells release sOB-R, supernatant of cultured placenta l cells was subjected to Western blot analysis. sOB-R was detected in the medium by the second day of culture and sOB-R release increased up to the fourth day of culture. Addition of leptin to the medium did no t affect expression of OB-R mRNA. However, 8-bromo cAMP inhibited both steady-state levels of OB-R mRNA and the amount of sOB-R protein in t he medium in a dose- and time-dependent manner. These results suggest that trophoblast cells differentiate, express, and release sOB-R both in vivo and in vitro and that cAMP is one of several potent regulators of sOB-R secretion by the mouse placenta. (C) 1998 Academic Press.