Transport of microspheres in the genital tract of the female rabbit.

Abstract

Experimental analysis of the influence of endogenous hormones on egg transport in the oviduct requires groups of animals in which the endocrine environment differs from that prevailing during the early postovulatory period. In order to measure transport in these animals, a substitute for the egg must be introduced. Eggs in cumulus obtained from donor rabbits (Noyes, Adams & Walton, 1959) or radioactive microspheres (Harper, Bennett, Boursnell & Rowson, 1960) have been used as substitutes, but both require surgical techniques and neither substitute is readily available. The present study was undertaken to see if dextran microspheres injected into the peritoneal cavity would act as useful substitutes for the egg in rabbits. Their uptake and transport by the genital tract was assessed under various endocrine conditions and the influence of their size on the speed of transport was also investigated. Female rabbits obtained at the local market were isolated and given 25 or 50 i.u. HCG intravenously to ensure good development of their genital tract. Thirty days later, they were either mated, ovariectomized or used in oestrus. The does were injected intraperitoneally with 2 ml of a sterile suspension of Sephadex G-100 (Pharmacia, Sweden) in Tyrode solution containing approx¬ imately 360,000 microspheres. Mated rabbits were injected 10 hr after coitus, ovariectomized rabbits 2 months after ovariectomy, and oestrous rabbits 30 days after HCG. Animals were killed 24, 48 or 72 hr after injection of Sephadex, and the entire genital tract was removed and dissected free of surrounding tissues. The ovi¬ ducts were divided in three equal segments. These segments, the uterine horns and the vagina were individually flushed with Tyrode solution to determine the presence and number of microspheres. The distribution of the eggs was also examined in the mated group. The microspheres in the flushings were counted under the low power of a stereomicroscope. In a few instances, all the microspheres obtained from individual segments were washed with Tyrode solution and photographed to measure their diameter from enlarged prints. The dia¬ meter of these beads in Tyrode solution (298 mosmol) was 130 + 60 µ (mean +