QUANTITATIVE COMPARISON BETWEEN OXYTOCIN AND FOUR RELATED NEUROHYPOPSIAL PEPTIDES ON THE HUMAN UTERUS IN SITU

Quantitative assays of four synthetic peptides related to oxytocin were carried out on the post partum human uterus in vivo by means of external tocography. The following activities (U/mg, means and standard errors) were found: isoleucine(8)-oxytocin 365+/-70, asparagine(4)-oxytocin 150+/-40, desamino(1)-oxytocin 1,030+/-300, serine(4)-isoleucine(8)-oxytocin 335+/-95. None of the conventional bioassay procedures proved to be fully reliable for predicting the oxytocic activity in man of peptides related to oxytocin. If the tocographically recorded effects of equipotent doses of the compounds are compared with those of oxytocin no qualitative differences can be observed.