Effects of Ehrlich Ascites Carcinoma Cells on the responses of non-pregnant and pregnant uterine smooth muscles of mice to oxytocin and acetylcholine

The effects of Ehrlich Ascites Carcinoma (EAC) cells on the responses of isolated uterine smooth muscles obtained from normal non-pregnant and pregnant mice to oxytocin and acetylcholine (ACh) were investigated. The contractions of normal uterine smooth muscles to oxytocin "0.1, 1 and 10 mU" and to ACh "0.1, 1 and 10 uM" were significantly reduced in the presence of EAC cells. On the other hand, induction of pregnancy in control non-tumor bearing mice significantly increases the sensitivity of the uterine smooth muscles to oxytocin as well as to ACh. In tumor bearing mice, the induction of pregnancy significantly reduced the sensitivity of the uterine smooth muscles to oxytocin and ACh when compared with the uterine muscles obtained from pregnant non-tumor bearing mice. The results of the present study indicate that the presence of tumor cells decreases the responses of the uterine smooth muscles to oxytocin and ACh, while pregnancy increases the uterine contractions induced by oxytocin and ACh. Furthermore, induction of pregnancy in tumor bearing animals reduces the responsiveness of uterine smooth muscles to oxytocin and ACh.