Ovine chorionic somatomammotrophin (oCS) production by isolated cotyledon cells from sheep in early and mid gestation : auto-regulation by recombinant oCS

We report the ability of sheep placental cotyledonary cells, isolated at diVerent periods of pregnancy (40 to 90 days) to produce ovine chorionic somatomammotrophin (oCS) in in vitro culture conditions. This oCS production increased gradually with stage of pregnancy. Endogenous oCS net production by isolated placental cells was increased, in a dose-dependent manner, by addition of recombinant oCS (roCS). This eVect was not observed after addition of recombinant ovine growth hormone. The roCS eVect was more potent on cells collected during early pregnancy. Specific immunoprecipitation of oCS revealed that roCS treatment was associated with an increased dosedependent incorporation of [ 35 S]methionine-[ 35 S]cysteine. These findings provide evidence that oCS may act in a paracrine/autocrine manner to up-regulate its own production during early gestation. We suggest that this autoregulation may be associated with morphological and functional diVerentiation of the trophoblast during the growth of the placenta.