Changes in the concentration of somatomedin-like activity in amniotic fluid and maternal plasma from rhesus monkeys during the last third of gestation.

Somatomedin-like activity (SLA) was measured in serial samples of amniotic fluid and maternal plasma from Rhesus monkeys (Macaca mulatta) using the porcine costal cartilage disc bioassay. Samples of both amniotic fluid and maternal plasma gave dose response curves which were parallel to the human plasma standard. Concentrations of SLA were consistently lower in amniotic fluid (0.42 +/- 0.02, mean +/- S.E.M., units/ml, n = 33) than in maternal plasma (0.60 +/- 0.03 units/ml, n = 31). No significant changes in concentrations of SLA with gestational age were found during the period studied (90-170 days of pregnancy). The presence of SLA in amniotic fluid is consistent with the possibility that somatomedin plays a role in the control of foetal or placental growth in the primate.