Dietary restriction alters the "in vitro" spontaneous or oxytocin-induced contractions of uterine smooth muscle from estrous rats. Possible participation of prostaglandins.

Rats subjected to a restricted-diet (50% of the normal intake for 15 days) presented a progressive reduction of body weight. The isometric developed tension (IDT) of uterine horns obtained from these animals during estrus exhibited greater initial (postisolation) values and a better constancy with time than preparations from normal-fed controls. The enhanced contractions were diminished after a refeeding period of 6 days as well as following the addition into the suspending medium of inhibitors of cyclo-oxygenase (indomethacin or acetylsalicylic acid). Cumulative dose-response curves to oxytocin documented a greater sensitivity in uterine horns from restricted-diet rats than in those from controls or refed animals. The output of prostaglandin (PG) E2 but not that of PGF2 alpha into the external solution was significantly higher (P less than 0.001) in the case of uterine tissue from restricted-diet rats than in normal fed controls. The findings suggest that changes in IDT evoked by partial starvation are associated with the enhanced generation of some PGs by the uterus.