Hormonal Control of Transport of Eggs in Cumulus Through the Ampulla of the Rabbit Oviduct

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Abstract
Newly ovulated eggs in cumulus, stained with toluidine blue, were transferred to the ampullae of the oviducts of (a) 36 mature rabbits 7 days after bilateral ovariectomy, and (b) 13 intact mature rabbits These rabbits received various doses of progesterone and/or estradiol benzoate (EB), dissolved in cotton seed oil and injected subcutaneously. The mean times (min.) for the eggs to move from the base of the infundibulum to the junction of the ampulla and the isthmus were recorded, and subsequently converted in relation to the length of the ampulla to the mean rates of transport (mm/min.). Ovariectomy decreased the mean rate of transport to 4.5[plus or minus]0.8 mm/min., and this was not significantly further decreased (2.8[plus or minus]0.4 mm/min.) by daily treatment with 2 mg progesterone. Treatment with 2 and 4 ug EB/day restored the rate of transport (8.4[plus or minus]0.9 and 10.0[plus or minus]0.6 mm/min., respectively) to the levels seen in estrous animals. Progesterone injections (2 mg), which were given 13 hr. before the observations on transport to ovariectomized animals receiving daily injections of 4 ug EB, failed to depress this response (9.8[plus or minus]1.0 mm/min.). In intact estrous animals given daily injections of 2 mg progesterone, a figure (5.7[plus or minus]0.4 mm/min.) similar to that seen in 2.5 day pseudopregnant animals was observed. However, 2.5 day pseudopregnant animals which had received daily injections of 4 [mu]g EB only gave a value (7.9[plus or minus]0.7 mm/min.) intermediate between those seen in estrous and in pseudopregnant animals. It is concluded that estrogen can stimulate and progesterone can depress the activity of the ampullar musculature, which in turn produces quicker or slower egg transport through the ampulla. It is not the level of estrogen or progesterone itself, but the relative levels of both hormones which determine the rate of egg transport.