[Role of endosalpinx in the oviductal environment]

The oviducal fluid and serum samples from rabbits were obtained daily during estrus and pseudopregnancy and were analyzed for electrolytes, steroid hormones and prostaglandins (PGs). The oviducal fluid volume reached its maximum (1.72 +/- 0.39 ml/day) 48 hours after hCG exposure and then declined gradually. Although the ratios of Na+/K+ and Ca++/Mg++ in the oviducal fluid did not change substantially throughout the observation period, the levels of K+ in the oviducal fluid were consistently 2.5 times greater than those in the serum. The concentrations of progesterone in the oviducal fluid were significantly smaller than those found in the serum. The levels of estradiol in the oviducal fluid were consistently elevated above the serum levels. The concentrations of PGF2 alpha in the oviducal fluid increased rapidly following ovulation and reached levels that were 10-14 times greater than those found in the estrus, whereas PGF2 alpha levels in the serum did not change significantly during the observation period. A significant difference between PGF2 alpha/PGE2 in the oviducal fluids (3.66 +/- 0.72) and serum (0.25 +/- 0.11) was observed at 24 hours after hCG. A surface morphologic study revealed a decrease in the number of ciliated cells, and an increase and expansion of secretory cells after hCG administration. The qualitative and qualitative differences between the oviducal fluid and serum suggest the involvement of secretory cells in the microenvironment for fertilization and preimplantation embryonic development.