[A bioassay for the testing of the oxytocic effect of hormone analogs of the neurohypophysis and the pineal body].

An improved bioassay for the testing of oxytocic compounds by the use of myometrium layer preparations has been developed and proved with synthetic oxytocin. The oxytocic activity of synthetic analogues was testes with this bioassay and compared to oxytocin. The myometrial layer preparation was demonstrated to be reliable, the vitality of the tissue is found for more than 8 hours. The sensitivity of the bioassay is found in the region of 10(-11) Mol/l oxytocin, the maximum of the stimulation of muscle strips varied from 5 X 10(-5) IU/ml to 10(-4) IU/ml oxytocin in the organ-bath. The concentration of the myometrium strips showed two different phases. Only the initial phase can be used for this bioassay. The calculation of the results was afforded planimetrically and by measuring of the concentration-maximum during the testing period. The synthetic hormone analogues [1-desamino-4-alpha-aminobutyric acid] lysine-vasotocin (2) and [4 alpha-aminobutyric acid] lysine-vasotocin had oxytocic activity and the myometrium was activated to contractions at 10(-8) Mol/1. The analogue 2 was 5-10 more active than 3. The contraction maximum for both analogues was found between 5 X 10(-6) and 5 X 10(-5) Mol/l. The induction of the concentration for both analogues varied with the factor 10(5).