Abstract
The time of production of the uterine luteolytic factor, which is considered to be derived from the endometrium following induced inflammation, was investigated in the cow.
By histological examination, it was found that inflammatory damage on the endometrium indu-ced by a single intrauterine injection of Lugol's solution (I : KI : H2O= 1 : 2 : 300) was repaired almost completely, 34 days after the treatment. To prevent the repair of the inflammatory damage to the endometrium, cows were treated successively with Lugol's solution twice a day at inrervals of 12 hours from Day 3, 5, or 7 to 9 of the estrous cycle (Day 0 =day of ovulation). The mean cycle length of these cows was reduced to 17.018.0 days. These cycle lengths were almost equal to those of the cow treated singly on Day 9 of the estrous cycle. When the successive dsily intra-uterine treatments from Day 3 to 9 of the estrous cycle were interrupted for 3 days, begining the day folliwing the first day of the treatment, and hence the reparation of the endometrium was allowed during this period, the mean cycle length was reduced to 10.0 days. This cycle length was almost equal to that of the cow treated singly on Day 3 of the estrous cycle. While, when the treatments were interrupted for 1 or 2 days, the mean cycle length became 16.5 days. This cycle length was almost equal to that of the cows treated successively. When cows were treated once on Day 13 of the estrous cycle, and retreated 4 to 8 days later, their cycle lengths were pro-longed in all cases which were retreated 4 days later and in half of them which were retreated 6 days later. In the remaining half of the cows in the latter group, and in all cows retreated 8 days after the first treatment, the cycle lengths remained normal.
These results indicated that the luteolytic factor might be derived from the endometrium dur-ing the reprartory process of inflammatory damages, or after completing it, and produced 34 days after the induction of the endometrial inflammation in the cow during the early luteal stage. The time of psoduction of this factor in the cow, during the late luteal stage, seemed to be some what delayed. Ferthermore, the luteolytic factor produced following the endometrial inflammation, should have an intensive character which could regress the corpus luteum within a priod as short as approximately one day.
