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 at two distinct endocrinological stages were analyzed electrophoretically. The quantitative relationships between the major macromolecular fractions were calculated from the densitometer scans. At pro-oestrus there was a marked increase in the total luminal proteins which was probably not due to transudation of serum into the lumen because of the presence of large amounts of two proteins, of approximate mol. wt 125,000 and 130,000, which were not detected in serum. Quantitative estimates of proteins of different molecular weight fractions in the fluids showed that there were considerable differences between the three 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 considerable lower amount of protein in the uterine lumen and qualitatively these proteins differed from those in serum and the uterine lumen at pro-oestrus.

PROTEIN COMPOSITION OF THE LUMINAL FLUID AND PROTEIN SYNTHESIS IN VITRO BY THE OVIDUCTS AND UTERI OF OVARIECTOMIZED, PRO‐OESTRUS AND 5‐DAY PREGNANT RATS

“…Previous studies have indicated that the protein content of uterine luminal fluid is considerably higher at pro-oestrus than during pregnancy (Surani, 1977a) and this has been confirmed by the present results. The differences in protein content of uterine luminal fluid after ovariectomy and during pro-oestrus and pregnancy (Day 5) were probably due to differences in endocrine status, namely high oestrogen levels during pro-oestrus as against high levels of progesterone and medium levels of oestradiol during pregnancy.…”

On the source of uterine 'luminal fluid' proteins in the mouse

“…Samples of such proteins are usually obtained by flushing the lumen (Surani, 1975(Surani, , 1977 Gore-Langton & Surani, 1976;Pratt, 1977;Aitken, 1977). I had been puzzled by the large amounts of material so obtained from mouse uteri on Days 4-5 of pregnancy, because at this time the lumen virtually disappears, the luminal epithelial surfaces coming into such close proximity that the microvilli of the opposing surfaces interdigitate or disappear (Mayer, Nilsson & Reinius, 1967;.…”

The blood-uterine lumen barrier and exchange between extracellular fluids

“…Oestrogens appear to be principal regulators o f IgA plasma cells to the uterus and upon uterine levels o f secretory component (Sullivan & Wira, 1981). Thus, the transfer o f IgA and IgG across the uterine epithelium in response to oestrogen occurs by two distinct mechanisms, one o f which (IgA) is specific and likely to require protein synthesis (Wira et ul., 1984) and the other (IgG) (Hall et al, 1977;Surani, 1977)…”

“…material which does not adsorb initially to the plasma membrane) (Morales & Hermo, 1983). Thus, endocytosis of this type has been suggested to participate in the reabsorption of uterine fluid from the lumen (Enders & Nelson, 1973;Parr & Parr, 1974, 1977. However, because mannose-specific binding sites for horseradish peroxidase have been described for various cells in the rat (Straus, 1983;Wilson & King, 1986), internalization of this protein might be more specific than previously considered.…”