Effects of passive immunization against estradiol on rabbit ovum transport

The role played by estradiol in control of ovum transport was studied in rabbits that were induced to ovulate by hCG stimulation. Withholding estrogen from target tissues during ovum transport by passive immunization with sheep anti-estradiol immunoglobulin (AE) resulted in accelerated oviductal transport and expulsion of ova from the uterus. The degree of accelerated transport was dependent on the duration of AE treatment. When AE treatment was started 24 h before hCG, fewer ova were recovered from the reproductive tracts at 72 h after hCG than were recovered from tracts of animals treated with a nonspecific immunoglobulin; the location of ova at 48 h after hCG was unaltered by this AE regimen. When AE treatment was started 72 h before hCG, fewer ova remained in the oviducts than were found in the tubes of controls at 48 h after hCG; and at 48 h after hCG, ova were found in the uteri of animals that had been treated with AE starting 72 h before hCG. When AE treatment was started 48 h before hCG, the position of eggs within the reproductive tract was not different from controls at 48 h after hCG. These observations support the concept that estrogen withdrawal is involved in the transport of ova through the oviduct of the rabbit, and suggest that the lack of estrogen secretion from the time of ovulation through the transport period is important in the control of normal ovum transport.