Uterine secretion in mammals: synthesis and placental transport of a purple acid phosphatase in pigs.

Abstract

A fluorescent antibody technique was used to study the site of synthesis, movement and steroid control of porcine purple acid phosphatase uterine protein in uterine and oviducal tissues on Days 0, 3, 6, 9, 12, 15 and 18 of the estrous cycle. Uterine, oviduct and placental tissues were obtained from pregnant gilts on Days 9, 15, 18, 20, 30, 50, 70 and 90 of gestation. In addition, uterine tissue was obtained from ovariectomized animals subjected to various steroid hormone treatments. The oviducal eoithelium and uterine surface and glandular epithelium showed various degrees of fluorescence at different stages of the estrous cycle with an apparent change in pattern coincidental with fluctuations in ovarian steroid levels. It was concluded that estrogen may be required for initiation of synthesis of this protein, but progesterone induced full synthesis and secretory activity. Enzyme assays performed on uterine flushings from each day of the estrous cycle support the immunofluorescent results. In pregnant gilts, oviducal and uterine surface and glandular epithelium showed fluorescence at all stages of gestation studied. A significant difference was observed in the pattern of fluorescence between uterine endometrium of early pregnancy and that of the corresponding stages of estrous cycle. As pregnancy progressed, placental areolae became strongly fluorescent, indicating absorption of uterine gland secretions by these structures. Inhibition of uterine secretory activity took place in association with rising estrogen levels toward the end of gestation. This study suggests that the purple acid phosphatase is synthesized and secreted by the uterine epithelial cells under the influence of progesterone and that placental areolae serve as sites of absorption and transport of this protein across the chorio-allantoic membranes and into the allantoic fluid where it is sequestered during pregnancy.