Decidua is a possible source of serum mouse soluble interleukin-6 receptor (msIL-6R): gestational profile of serum msIL-6R concentration.

The serum concentration of msIL-6R of 10 weeks old virgin ICR mouse assessed by a RIA was 45.6 +/- 6.6 ng/ml. The serum msIL-6R concentration of the pregnant mouse mated at 10 weeks of age was 41.2 +/- 3.0 ng/ml on day 7 of pregnancy. The serum concentration gradually increased during gestation and reached peak on day 17 of pregnancy (149.1 +/- 13.7 ng/ml). On the third day of the puerperium, the serum msIL-6R concentration of the mother from which the pups had been removed on the day of delivery was decreased to the level of that on day 7 of pregnancy. IL-6R mRNA level in the decidua significantly increased during mid and late gestational stages. msIL-6R was detected in the medium of cultured decidual cells (8.03 +/- 0.28 ng/ml), but not placental cells. Western analysis for msIL-6R using the conditioned medium of the cultured decidual cells resulted in a single band at approximately 45 K. To find out a biological role of msIL-6R during gestation, placental cells were incubated with mIL-6 and msIL-6R, and mPL-I concentration in the medium was assessed by RIA. 2.5 nM mIL-6 did not affect the secretion of mPL-I in placental cells; however, addition of msIL-6R resulted in a significant stimulation of mPL-I secretion. These results suggest that serum msIL-6R, which is likely to be secreted from decidua, may play an important role during gestation.