Relationship between changes in volume of the oviductal fluid in the ampulla and the descent of ovulated eggs from the ampulla to the isthmus in mice.

ABSTRACT

Follicular growth and ovulation were induced in mice by administration of pregnant mare serum gonadotrophin (PMSG) followed 2 days later by human chorionic gonadotrophin; the day of PMSG injection was designated as day 0. The volume of the ampulla was measured and the location of the ovulated eggs determined at 0600, 1000, 1400, 1800 and 2200 on day 3, and at 0200 and 0600 on day 4. The volume of the ampulla and hence oviductal fluid, peaked at 1400 on day 3 and then declined. In all oviduct samples taken up to 1400 on day 3, eggs were found exclusively in the ampulla. Thereafter, an increasing number of eggs were observed in the isthmus. Thus, the migration of eggs from the ampulla to the isthmus was concurrent with the decrease in oviductal fluid volume. The peak in the volume of oviductal fluid seen at day 3 is likely to coincide with the opening of the ampullary-isthmic junction of the oviduct.