Qualitative and quantitative examination of the proteins of rat uterine luminal fluid during pro-oestrus and pregnancy and comparison with those of serum

Abstract

Rat serum and uterine luminal proteins in 2 distinct endocrinological stages were analyzed electrophoretically. Quantitative relationships between major macromolecular fractions were calculated from densitometer scans. At proestrus there was a marked increase in total luminal proteins which was probably not due to transudation of serum into the lumen because of presence of large amounts of 2 proteins, of approximate MW 125,000 and 130,000 which were not detected in serum. Quantitative estimates of proteins of different MW fractions in the fluids showed that there were considerable differences between the 3 fluids, indicating that the hormones do not merely induce a free passage of serum proteins into the lumen. On day 5 of pregnancy, there was a considerably lower amount of protein in uterine lumen, and qualitatively these proteins differed from those in serum and the uterine lumen at proestrus.