Alberta Pork Research Centre/ Department of Agricultural, Food and Nutitional Science, 4-10 AgFor Centre, University of
Alberta, Edmonton, Alberta, T6G 2P5
Almeida et al. (poster, this meeting) recently showed that nutritional restriction of gilts late in the estrous cycle results in a lower embryonic survival, correlated with lower progesterone concentrations immediately after ovulation. Other studies in gilts (Pharazyn et al., CJAS 71:949-952, 1991; Jindal et al., JAS 74:620-4 , 1996; Jindal et al., JAS 75:1063-70, 1997) and in sows (Jindal, 1996, Ph.D. Thesis; Clowes, 1993, Ph.D. Thesis) have also shown that differences in circulating progesterone in early pregnancy may mediate nutritional effects on embryo survival and thus affect litter size. During this critical window of time the embryo resides within the oviduct, and lowered steroid concentrations in this period may affect the oviductal environment.
The oviduct plays an important role in reproduction as the site of gamete transport, fertilization and early embryonic development. The oviduct secretes proteins that have been shown to adhere to sperm and oocyte membranes and become incorporated into the early cleaving embryo. The expression of these oviduct proteins is thought to be steroid induced, which suggests that differences in steroids during the peri-estrous period may affect the quality of the oviductal environment. However, steroid concentrations in the oviduct circulation are affected by a sub-ovarian counter-current system. Although peripheral progesterone concentrations in situations where nutrition affects embryo survival are known, it is necessary to determine the concentrations of steroids in the counter-current system and whether they affect oviduct proteins.
The objective of this study is therefore, to determine how manipulating steroid levels in the oviduct, changes the pattern of secretion of oviduct proteins. The model used was a unilaterally ovariectomized gilt for comparison of high and low oviductal concentrations of steroid in the same animal. Oviductal, peripheral and mixed ovarian venous blood were assayed for progesterone and estradiol concentrations. The oviduct proteins will be visualized using 1D SDS-PAGE electrophoresis and compared within animal.
Initial results show that progesterone concentrations were different between oviductal veins ipsilateral and contralateral to the remaining ovary, demonstrating the potential for different steroid environments to affect oviductal protein secretion.
Implication: Insight into the control of oviduct protein secretion by progesterone may help elucidate progesterone mediated affects of nutrition on embryonic survival.