The transport of ova in relation to the dosage of oestrogen in ovariectomized rabbits.

Abstract

SUMMARY In order to determine what part the level of oestrogen in the body might play in the passage of ova through the female reproductive tract, 1249 freshly ovulated ova from donor rabbits were transferred into the uterine tubes of seventy-four ovariectomized recipients, fifty-three of which had previously been treated for 5–18 days with small daily injections of oestradiol benzoate. From 10 to 78 hr after transfer, 41% of the ova were recovered from the uterine tubes, 9% from the uterine horns, and 23% from the vaginae of the recipient animals. Twenty-seven% of the ova were lost. The rate of ovum transport varied widely between similarly treated animals, and between the right and left sides of the reproductive tract of the same animal. Larger proportions of ova were retained in the uterine tubes, and smaller proportions in the uterine horns as the oestrogen dose was increased. The great variability in the stage of cleavage and in the thickness of the mucin coat of ova recovered from the uterus and vagina suggested that the ova might be widely dispersed through the uterine tubes and that they probably pass out of the uterine tube at widely different periods of time. Evidence is presented that ovum transport in ovariectomized rabbits with or without oestrogen treatment is very irregular, that ova may be ejected from either end of the uterine tube at almost any time after transfer, and that ova are not normally retained in the uteri of such animals. Approx. 1 μg oestradiol benzoate administered daily for 5–10 days was necessary to maintain the uterine weight of ovariectomized rabbits at about the same level as that in intact oestrous rabbits, and also to reduce the variability in egg transport observed in control and ovariectomized animals.