Localization and function of tyrosine-phosphorylated protein in pig oocytes

Localization (and profiles) of tyrosinephosphorylated proteins in female reproductive organs of adult rats

Objective

Tyrosine phosphorylation is an essential process in many biological systems, including the male reproductive system. The presence of tyrosine-phosphorylated (TyrPho) proteins has been well documented in male reproductive organs, but research in fertile females is still limited.

Methods

The ovary, oviduct, and uterus of adult female Sprague-Dawley rats in the estrus phase were used to localize TyrPho proteins using an immunohistochemical technique. These proteins were separated and their expression patterns were examined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis and Western blot analysis, respectively.

Results

TyrPho proteins were localized in the cytoplasm of the oocyte except the antral fluid; in the granulosa cells, theca cells, and stromal cells of the ovary; at the apical surface of oviductal epithelial cells; and in the basal epithelium and submucosa of the uterine wall. Moreover, we found that 72-, 43-, and 28-kDa TyrPho proteins were localized in the ovary, while 170-, 55-, and 43-kDa proteins were localized in the oviduct. In the uterus, we detected four major bands, corresponding to 61-, 55-, 54-, and 43-kDa TyrPho proteins.

Conclusion

Given that these TyrPho proteins were found in major reproductive organs in the estrus phase, these proteins may play important roles in female fertility.

Effects of the estrous cycle on the efficacy of oocyte collection and in vitro embryo production in Duroc-breed

Collection efficacy and in vitro embryo developmental ability of oocytes obtained from Duroc-breed ovary donors at different stages of the estrous cycle (days 6, 12 and 16 after estrus) were performed. The numbers of collected oocytes did not differ significantly among the different estrous cycle groups (total 72-90 oocytes per gilt). However, the blastocyst rates of oocytes collected on days 12 and 16 (9.2% and 19.4%, respectively) were significantly higher than those on day 6 (1.1%). More oocytes were obtained on day 16 from small follicles (<2 mm in diameter; 85.3 oocytes per gilt) than from medium-sized (≥2-<6 mm) and large (≥6 mm) follicles (17.5 and 12.8 oocytes, respectively). The blastocyst rates in both the medium-sized and large follicle groups (20.0% and 19.2%, respectively) were significantly higher than that in the small follicle group (6.3%). The blastocyst cell numbers in both the medium-sized and large follicle groups (39.4 and 43.3 cells, respectively) were significantly higher than that in the small follicle group (30.6 cells). The results suggest that oocyte collection from cycling Duroc pigs can be carried out efficiently from the late luteal to follicular stage. Those oocytes collected from medium-sized and large follicles show better embryo development.