Vasopressin effects on isolated non-pregnant myometrium and uterine arteries and their inhibition by deamino-ethyl-lysine-vasopressin and deamino-ethyl-oxytocin.

The contractile effects of lysine- (L) and arginine- (A) vasopressin (VP) on isolated non-pregnant myometrium and uterine arteries and the inhibition of these actions by two analogues of posterior pituitary hormones, deamino-ethyl-LVP (dE-LVP) and deamino-ethyl-oxytocin (dE-OXY) were investigated. Both AVP and LVP effectively stimulated the smooth muscle preparations. The threshold dose for both agonists was about 2 ng/ml of bath fluid and a maximal response was obtained with approximately 75 ng/ml. No distinguishable effect was produced by dE-LVP and dE-OXY alone, but when given before the agonists in concentrations of 150 or 300 ng/ml, dose-dependent inhibition of the contractions was seen. The inhibition of the uterine artery responses was always greater than the inhibition of the effects on myometrial activity and dE-LVP appeared to have stronger antagonistic effects than de-OXY on the myometrial responses to the agonists. The inhibition of the myometrial and uterine artery responses to AVP could explain the therapeutic effect of dE-OXY recently found in primary dysmenorrhoea, where increased VP secretion seems to be of aetiological importance.