THE EFFECTS OF OESTRADIOL-3,17β ON TUBAL TRANSPORT IN THE LABORATORY MOUSE

SUMMARY Pregnant mice received varying doses of oestradiol on days 1–3 of pregnancy, or on day 1 or day 2 only. The effects of oestradiol on tubal transport depend largely on the time of treatment rather than the dose of oestradiol. Treatment with 1·6 μg. on day 1 when the ova were still in the ampulla caused retention of all ova in the oviduct until day 4—many of these tube-locked ova were retained in the ampulla, apparently because of prolonged closure of the ampulla-isthmus junction. Treatment with 0·4 μg. on day 2 when all ova were in the isthmus caused premature entry of ova into the uteri and reduced the recovery of ova by over 50%. Ligation of various parts of the tract and ovum transfer studies showed that this loss of ova is due to accelerated transport from the isthmus to the uterus and vagina. These effects on tubal transport were not reversed by concurrent administration of progesterone. Tubal retention was associated with delayed development of the blastocoele but these ova implanted normally after ovum transfers.