Periovulatory glycoprotein secretion in the macaque fallopian tube

Anatomic demonstration of a specific midcycle fallopian tube secretion has been sought by transmission electron microscopy in the Macaca mulatta fascicularis with a method of in vivo perfusion-fixation that includes the polycation alcian blue (plus glutaraldehyde) to precipitate and stabilize anionic extracellular secreted glycoproteins. Of nine monkeys entered into the study, six ovulated regularly. With the help of daily plasma total estrogen radioimmunoassays and serial laparoscopies, these six monkeys were killed and the pelvic organs were perfused at specific times in the menstrual cycle: the midfollicular phase (one), during the midcycle estrogen peak immediately before ovulation (one), 24 hours after ovulation (one), 2 to 4 days after ovulation (two), and premenstrually (one). The other three monkeys were oophorectomized and were treated with estradiol benzoate, 10 micrograms/kg/day for 7 days (two), or with estradiol benzoate, 10 micrograms/kg/day for 7 days, and progesterone in oil, 1 mg/kg/day from day 3 to day 7. Evenly distributed, granular, precipitated material was found in the isthmic lumen both immediately before and 24 hours after ovulation (and in the two oophorectomized, estrogen-treated monkeys, both of which had plasma total estrogen levels that exceeded those of preovulatory monkeys); this would coincide with times of sperm ascent through the isthmus, ovulation, and fertilization and with the time of temporary impedance of the ovum's normal transport to the uterus, known to occur at the ampullary-isthmic junction. No substantial precipitable secretion was found in the ampulla at any stage of the cycle, in the isthmus before the midcycle estrogen rise, or 48 hours or more after either ovulation or initiation of progesterone treatment. These observations indicate that, in the primate fallopian tube, the unique ability of the isthmus to transport spermatozoa and ova in opposite directions sequentially is related temporally (and perhaps causally) to the presence and absence, respectively, of specific isthmic luminal secretions. The biochemical basis for this isthmic property may lie in the expected highly expanded state of acid mucus glycoproteins in the secretions.