Radiolabelled rat uterine luminal proteins and their regulation by oestradiol and progesterone

Abstract

Radiolabelled uterine luminal proteins were obtained 6 h after instillation of 5--10 muCi [35S]methionine into the lumen of each uterine horn of rats. The proteins were analysed electrophoretically on 6% polyacrylamide gels and incorporation of the precursor into the separated proteins was estimated in 0-18 cm gel slices by scintillation spectrometry. Major incorporation was obtained on Day 5 of pregnancy in a group of proteins of approximate mol. wt 3 X 10(4), 4-5 X 10(4) and 5-5 X 10(4) and in proteins of mol. wt 8--10 X 10(4). During pro-oestrus, substantial incorporation of the precursor occurred in a group of protein of mol, wt 13-5 X 10(4), 12-5 X 10(4) and 7-5--8-0 X 10(4) and slight incorporation in proteins of mol. wt 4-5 X 10(4). These changes were mimicked in ovariectomized females by injections of appropriate steroids: progesterone and oestradiol were necessary to induce the proteins detected during pregnancy, oestradiol alone was able to reproduce the changes observed at pro-oestrus. The proteins in the lumen appear to be of uterine origin because radiolabelled serum proteins were not detected in the lumen after an i.p. injection of the isotope. Also, labelled proteins were detected in the horn receiving the isotope but not in the contralateral horn injected with saline. Cycloheximide, given i.p. simultaneously with the isotope but not in the contralateral horn injected with saline. Cycloheximide, given i.p. simultaneously with the isotope, suppressed synthesis of uterine proteins.

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

“…In particular, we were unable to identify on Coomassie-stained gels two major non-serum proteins of 125 and 130 K which their study indicated were characteristic of pro-oestrus uterine luminal fluid. Whereas the synthesis and secretion of these two proteins were evident with radioactive methionine instilled into the uterine lumen in vivo (Surani, 1977b), synthesis of these proteins in vitro was not clearly evident in our studies. The reason for this discrepancy is not readily apparent.…”

“…For instance, Lejeune et aL (1982) identified 9 peptides from a total of 800 whose synthesis was selectively modified during artificial decidualization following progesterone and oestradiol treatment of ovariectomized rats, whilst Mulholland and Villee (1984) identified relative changes in the synthesis of 16 proteins between pro-oestrus and day 6 of pregnancy. In an analysis of radioactive secretory proteins resulting from instillation of ^^S-methionine into the uterine lumen in vivo, Surani (1977b) found major incorporation of isotope into proteins of 30, 45, 55 and 80-100 K on day 5 of pregnancy, whereas at prooestrus the major incorporation was into proteins of 75-80, 125 and 135 K. Moreover, the administration of either oestradiol plus progesterone or oestradiol alone to ovariectomized rats induced the pattern of synthesis appropriate to pregnant and pro-oestrus rats, respectively. In a more recent study, Komm et aL (1985) identified 2 proteins of 65 and 104 K whose synthesis and secretion in vitro are specifically stimulated by oestrogenic treatment of ovariectomized rats.…”

The Effect of a Single Dose of Human Chorionic Gonadotropin at Proestrus on Embryonic Mortality, Fetal Growth and Gestation Length in the Rat

“…In the rat, an estrogen signal is required around days 3-4 of pregnancy to initiate implantation at day 5 [15,16]. Steroids are well-known regulators of protein secretion in the uterus [ 17,18]. hCG may disturb the ste roid metabolism, and this may lead to a less than optimal timing of the uterine protein secretion in relation to embryonic age, what may again result in an uterine environment that is hostile to the implantation of blasto cysts [19].…”

Protein synthesis by bovine chorion and uterine endometrium during the period of implantation

“…All tissues were stained with uranyl acetate and lead citrate except for Fig. 6 (Surani, 1977) and mouse (Fishel, 1979) (Flint, 1970). Rice (1978) examined the relationship between the concentration of leucine in the medium and its rate of incorporation into porcine blastocyst tissue.…”