An appraisal of the mouse uterine weight assay for the bioassay of chorionic gonadotrophin in the macaque term placenta.

The results obtained in this investigation have shown that the increase in uterine weight of 21-day-old mice, injected with monkey CG, was affected significantly by the number of injections made, the interval between injections and the time of autopsy after the first injection. Failure to take account of these factors may explain why some investigators, using the increase in mouse uterine weight as the index of response, do not find CG in macaque placentae after the 10th week of pregnancy. The present investigation confirmed that extracts of term placentae from rhesus and stump-tailed monkeys contained measurable amounts of CG whose biological activity could be neutralized by an anti-hCG serum.