Relation of Oestrin and Pregnancy Urine Hormone in Influencing Uterine Motility. ∗

The relationship which exists between oestrin and progestin in regulating uterine motility suggested the possibility of a similar relation between oestrin and pregnancy urine hormone. Reynolds and Friedman 1 and Reynolds 2 have shown that the uterine motility of the unanesthetized rabbit, as recorded by the uterine fistula method, is inhibited by intravenous injections of pregnancy urine hormone. The inhibition of uterine motility induced by pregnancy urine hormone in either normal rabbits or castrated rabbits treated with oestrin, is somewhat similar to that obtained with progestin and is characterized by either a disturbance in normal rhythm, a diminished height of contraction or complete quiescence. The inhibition is transitory in the castrated rabbit and the motility returns to normal usually within 24 hours. It will be shown that if a castrated female rabbit is given sufficient amounts of oestrin, the pregnancy urine hormone in doses ordinarily capable of inhibiting uterine activity, is unable to act.

In the first series of experiments, uterine fistulae were prepared, according to the technique of Reynolds, 3 in 12 adult female rabbits in heat and records of uterine motility were taken 3 to 4 days after the operation. Six to 9 hours after intravenous injections of varying doses of an extract of pregnancy urine (Follutin)† or other gonad stimulating urines, 11 of the 12 rabbits responded by complete inhibition of uterine motility, Table I. Ovulation occurred in all rabbits but one, in which a loss of activity of the hormone accounted for the failure of ovulation and inhibition of motility. These results confirm Reynolds. 2

In the second series of experiments, 9 adult female rabbits were castrated and the uterine fistulae prepared.