SECRETION OF RIBOFLAVIN BY THE PORCINE UTERUS la

Summary A study of 10 mature crossbred, ovariecto- mized gilts was conducted to determine whether riboflavin secretion by porcine uteri is regulated by estrogen and progesterone. A second experi- ment was performed to determine whether secretion of riboflavin occurs in pregnant animals in a temporal and quantitative pattern similar to that in nonpregnant animals. In the hormonal induction experiment, it was found that animals receiving daily injections of estrogen for 5 days followed by a daily injec- tion of a combination of estrogen and pro- gesterone were able to secrete riboflavin in quantities comparable to those secreted by intact animals. Additionally, it was found that the secretion of riboflavin appeared to be related to onset of treatment with progesterone in that riboflavin secretion increased in a time-related pattern after the beginning of progesterone treatment. In a second experiment, pregnant animals secreted riboflavin in their uterine secretions in quantities and in a time pattern similar to those found in nonpregnant animals. Nonpregnant gilts in the 8th day of an estrous cycle were used for comparison to the pregnant animals in this experiment, and the quantity of riboflavin uterine secretions in the nonpregnant animals was similar to that found on day 8 in the pregnant animals. Taken together, these two experiments indicate that riboflavin is secreted under hormonal regulation by the uterus in both pregnant and nonpregnant pigs at a precisely controlled time in the progestational phase. (Key Words: Riboflavin, Swine, Uterus, Pro- gesterone, Pregnancy, Ovariectomy.)