This thesis presents a combined approach using ultrastructural, electrophysiological and endocrinological methods to investigate factors which control myometrial contractility in vivo in the period of time around parturition, in an attempt to integrate various recent research findings. These findings indicate the importance of steroid hormones, prostaglandins and myometrial gap junctions in the control of myometrial contractility during pregnancy and labor. Our study in pregnant ewes shows the relationship between the presence of gap junctions during labor and the observed increase in myometrial contractility. Gap function formation, Which facilitates the spread of electrical activity across the myometrium, appears to be associated with enhanced coordination of contractile activity of the myometrial smooth muscle cells. The increase in the number of gap junctions which occurs in all species investigated, also in humans, seems to be a necessary step in the initiation of parturition. The results of our study, as well as those of studies by others in sheep, rats and rabbits, indicate that gap junction formation is regulated and modulated by steroid hormones. Progesterone inhibits and estradiol stimulates the formation of gap junctions. Since investigation in vivo of the regulation of gap junction formation by steroid hormones, and by other factors such as prostaglandin synthesis, causes considerable difficulties in pregnant animals, we developed a nonpregnant animal model in which several factors could be manipulated more easily

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This work was supported by grants from theN ether lands Organization for the Advancement of Pure Research (ZWO), the Medical Research Council of Canada, and Sarva-Syntex Nederland
H.C.S. Wallenburg (Henk)
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam

Verhoeff, A. (1985, November 27). Myometrial contractility and gap junctions : an experimental study in chronically instrumented ewes. Retrieved from