The technique of tracing the movement of 'artificial eggs' (radioactive spheres) by autoradiography was used to study the effects of progesterone and oestrogen either alone, or in combination, on egg movement through the reproductive tract of ovariectomized rabbits.
Ovariectomy was performed 7 days before the transport experiments, except in one treatment group when it was done 35 days previously. The animals were autopsied at 8, 24, 48 or 56 hr. after insertion of the spheres into the ampullae of the Fallopian tubes. There were five or more animals in each group except one.
The effects of various hormonal replacements were studied. It was found that removal of the ovaries, whether 7 or 35 days before the transport experiments commenced, caused extremely irregular movement of the spheres through the Fallopian tube. Marked differences were recorded between the behaviour of the spheres in animals ovariectomized for the shorter as compared with the longer period.
None of the hormonal treatments produced normal movement of the spheres through the Fallopian tube. Progesterone delayed movement of the spheres through the ampulla very markedly, but if the spheres reached the isthmus they passed into the uterus on all occasions. Neither the isthmus nor the utero-tubal junction in animals so treated proved a barrier to the movement of the spheres into the uterus. Movement of the spheres through the uterus of these animals was inhibited, and most of the spheres recovered were found in the half of the uterus nearest to the utero-tubal junction.
Oestradiol benzoate, in the dose administered, had an accelerating effect on the passage of the spheres through the tube, and also through the uterus. Some spheres were found to have entered the vagina in three out of the four time-groups studied. It was observed that despite the accelerating effect of oestrogen on the movement of the spheres through the Fallopian tube a certain percentage, even after the longest interval studied, was trapped at the junction of the ampulla and the isthmus.
The two groups treated with oestrogen and progesterone in combination tended to produce results similar to those observed after treatment with either progesterone or oestrogen alone, depending on which hormone was dominant.
It is concluded that the amount of oestrogen present is critical in ensuring rapid transport through the ampulla, but that a proper balance of oestrogen and progesterone must be maintained to ensure retention of the spheres or eggs in the isthmus until the correct time for entry into the uterus. It is clear that this pattern of egg movement through the Fallopian tube cannot be re-created by fixed daily doses of progesterone and oestrogen.
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