Investigations into the spontaneous contractile activity of isolated human uterine arteries in vitro.

Uterine artery strips and myometrium from the same uterus were placed in the same water bath and their rates of contractile activity were registered simultaneously. Isolated strips of uterine arteries showed spontaneous contractile activity--a phenomenon especially marked in the secretory phase of the cycle. In the proliferative phase spontaneous contractions of blood vessels, characterized by low intensity and a frequency of three contractions in 10 minutes, were seen. In the secretory phase the contractions were of lesser intensity and higher frequency. The rhythm of contractions of the myometrial vessels was markedly different from the spontaneous activity of the myometrial strips. In discussion of the results, special attention has been paid to the role of spontaneous contractility of myometrial vessels in the contractile activity of the whole uterus.