The role of cilia in fertility: an evaluation by selective microsurgical modification of the rabbit oviduct.

Fertility, ovum transport, and ciliary activity were examined in 35 rabbits after either unilateral microsurgical reversal or double transection (surgical controls) of 1 cm. segments of distal, middle, or proximal ampulla. Fertility was also examined following similar segmental reversal at the level of the distal and proximal isthmus in eight additional rabbits. Reversal of 1 cm. segments of distal, middle, or proximal ampulla effectively prevented pregnancy. In contrast, control animals that underwent double transection without reversal experienced unaltered fertility. Reversal of 1 cm. segments of distal or proximal isthmus was also consistent with normal fertility. Ova placed on the fimbrial surface of oviducts that had undergone ampullary segmental reversal were arrested at the distal anastomosis of the reversed segment. When mechanically displaced into the reversed segment, such ova were transported toward the ovary and were again arrested at the distal anastomosis. Transampullary transport of ova was normal in doubly transected controls. Ova were transported across both anastomosis sites to the ampullary isthmic junction. Studies of ciliary activity confirmed that cilia within reversed segments of ampulla beat in the ovarian direction, counter to that in the rest of the oviduct. Direction of ciliary beat remained unaltered in surgical controls. These experiments demonstrate a critical role of tubal cilia in ovum transport through the rabbit ampulla. In contrast, other mechanisms control ovum transport into and through the tubal isthmus.