Effects of intrauterine infusion of iodine solution, on the estrous cycle of the cow. I. Modification of the estrous cycle length and inflammatory response of the endometrium to the treatment
In our earlier report, it has been shown that the estrous cycle length of the cow can be shortened by inserting rubber tube into the uterine horn during the first half of the cycle. Our recent experiments have demonstrated that the intrauterine injection of a viscous gel-like substance at early luteal phase can accelerate the regression of the bovine corpus luteum and, on the contrary, the treatment at late luteal phase can delay it. In the latter experiments, we have also found that the endometritis is induced temporarily by this treatment. From these results, it is supposed that the inflammatory changes of the endometrium may be related to the life span of the corpus luteum.The purpose of the work presented here is to investigate 1) the effects of intrauterine infusion of iodine solution as an irritant on the estrous cycle length of the cow and 2) the irritating effects of the treatment on the bovine endometrium.1) Experiment 1. The effects of intrauterine infusion of iodine solution on the estrous cycle length. Two preparations of iodine i.e. Lugol's solution and solution of polyvinyl pyrrolidone (PVP-I) were used. They were injected into the uterus through the cervix by using a sterilized metal catheter. The treatments were performed on a total of 43 cycles of 11 cows including 9 Japanese beef cows and 2 Jersey cows. When an animal was used successively, she was retreated after it was confirmed that the previous treated cycle had been followed by 1-3 cycles of a normal length. After the treatment, involution of the corpus luteum, development of the follicle and ovulation were examined via rectal palpation at 1-3 days interval. The cervical mucus stained with Giemsa was also examined microscopically. The day on which ovulation occurred was considered as Day 0 of the cycle.i) Intrauterine infusion of Lugol's solution on Day 3 : Five to fourty ml of Lugol's solution at various concentrations was injected into the uterus of a total of 18 cows on Day 3. The results were shown in Table 1. In 14 of the treated animals, ovulation occurred 6-13 days (av. 8.6±1.9 days) after the treatment and the mean length of the treated cycles was reduced to 11.6±1.9 days. Estrouscycles of the remaining animals were of a normal length in 3 and fairly lengthened in 1. It was also noticed that Lugol's solution diluted 10-20 fold by distilled water was effective enough to modify the cycle length.ii) Intrauterine infusion of Lugol's solution on Day 16 : In all of 3 animals treated with 40ml of original Lugol's solution on Day 16 (late luteal phase), ovulation occurred 9-11 days (ay. 10.0±1.0 days) after the treatment and the mean length of the treated cycles was lengthened to 26.0±1.0 days.iii) Intrauterine infusion of PVP-I solution on Day 3 : A total of 21 cows was treated with 1.5-40.0ml of 2.5-100.0mg/ml solution of PVP-I on Day 3. The results were shown in Table 2. In 15 animals injected with 2.5-40.0ml of PVP-I solution, ovulation occurred 6-10 days (av, 7.8±1.3 days) after the treatment and the mean length of the treated cycles was reduced to 10.8±1.3 days. Estrous cycles of the remaining 6 animals were of a normal length. PVP-I solution at the concentration of at least 10mg/ml was noticed to be effective to modify the cycle length.iv) Responses of cervical mucus to the intrauterine treatment : On 19 estrous cycles included in Experiment 1, cervical mucus samples collected before and after the treatment (on Day 3) were examined microscopically. The results were shown in Fig. 1. For several days after the treatment, the cervical mucus was cloudy and a large number of neutrophile leucocytes and epithelial cells and a small number of eosinophille leucocytes were observed in almost all of 13 animals in which estrous cycles were shortened after the treatment.