Investigation of the role of smooth muscle function in egg transport in the mouse oviduct.
The time course of egg transport along the mouse oviduct is important for successful implantation to occur. It is generally accepted that variations in the innate contractile activity of the oviduct musculature regulate the rate of egg transport, but the controlling mechanism behind these changes in muscular activity is unclear. This study investigated the role of calcium ions in oviduct smooth muscle function and the regulation of egg transport. A variety of methods were utilized including: a new in vitro technique, which allowed observation of egg movement and muscle activity in a controlled environment, in vivo measurement of transport rates and measurement of oviduct calcium ion content; and the effects of pharmacological agents, ovarian hormones, ovariectomy, and ligation and cauterization of the uterus from the oviduct on egg transport and oviduct calcium levels. The results indicate that the concentration of calcium could play an important role in the regulation of oviduct contractility and egg transport. A definite pattern of calcium ion concentration changes occurred during normal egg transport, and a close correlation was found between the effects of pharmacological stimuli on the rate of egg transport and on oviduct calcium concentrations. There was little evidence to support the concept of control of egg transport by post-ovulatory ovarian hormones, but pre-ovulatory progesterone levels may be important. If this is the case, variations in the contractile activity of the oviduct could perhaps be mediated through progesterone-induced changes in tissue calcium content or distribution, but further study is needed to clarify such a relationship.
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