EFFECTS OF VITAMIN D ON THE UTERINE MOTILTY OF RABBIT IN VIVO

The present investigation was undertaken in order to elucidate the effects of vitamin D on the uterine motility and interrelationship between vitamin D and ovarian hormones. Uterine motility was recorded kymographically in conscious animals with the help of small balloon inserted through the fistulae. The results obtained are as follows: 1) A single intramuscular injection of vitamin D of 10,000 or 50,000 i.u. per kg body weight caused an increase in the uterine motility lasting 3 to 4 days, and then gradually was brought to its inhibition. 2) Daily intramuscular administration of ,5,000 or 10,000 i.u./kg for about 40 days caused an increase in the uterine motility for about first 2 weeks and later the motility was gradually suppressed. When, 50,000 i.u./kg was given daily, uterine activity was strongly inhibited from the beginning. 3) When vitamin D and estrogen were administered simultaneously, the increase in the frequency and amplitude of uterine contractions was observed. This seems that vitamin D has a synergetic action to estrogen. 4) The administration of progesterone with vitamin D caused an inhibition of the uterine motility in the beginning, but this inhibitory effect disappeared gradually with the prolongation of the period of administration. This suggests the antagonistic action of vitamin D against progesterone. 5) The senstivity of the uterine motility for oxytocin well correlated with the promoting action of vitamin D.