Regulation of msIL-6R secretion by mIL-6 and 8-bromo cAMP was examined using primarily cell culture of mouse decidua. Mouse decidua on day 11 of pregnancy was digested by collagenase and decidual cells were cultured for up to 3 days. Addition of mIL-6 and 8-bromo cAMP resulted in significant inhibition of msIL-6R secretion from cultured mouse decidual cells by the 2nd day in culture. The effects were dose-dependent and the lowest concentrations of mIL-6 and 8-bromo cAMP which cause significant inhibition of msIL-6R secretion were 250 pM and 50 microM, respectively. Northern blot analysis indicated that treatment of decidual cells with 8-bromo cAMP significantly decreased the steady-state level of mIL-6R mRNA. However, treatment of decidual cells with mIL-6 did not affect the steady-state level of mIL-6R mRNA. These results suggest that mIL-6 decreases msIL-6R secretion without changing of the steady-state level of mIL-6R mRNA, and that cAMP is one of the second messengers in mouse decidual cells involved in this down regulation of msIL-6R secretion.