Properties of an estrogen-induced hydrolytic enzyme from mouse uterus

Rat proestrus uterine fluid contains a large molecular-weight protein complex with metalloendopeptidase activity

A neutral metalloendopeptidase has been identified in the secretion of the rat proestrous uterus. The native form of the enzyme secreted in the uterus is a high-mol-wt protein complex, which barely migrates in 3% native polyacrylamide gel electrophoresis. In 2% SDS, the enzyme resolves into 380-, 210-, and 110-kDa subunits. The 380- and 210-kDa proteins demonstrate peptidase activity in SDS-PAGE as detected by an enzyme overlay membrane impregnated with Suc-Ala-Ala-Phe-AFC. The uterine peptidase is substantially inhibited by EDTA, EGTA, 1,10 phenanthroline, thiorphan, DTT, and sodium dodecyl sulfate (SDS). The inhibition by 1,10 phenanthroline is reversed by CO2+. The uterine enzyme has a pH optimum of 7.0, and readily hydrolyzes acetyl tetraalanine and Suc-Ala-Ala-Leu-pNA by releasing alanylalanine and Leu-pNA, respectively. Kinetic analysis of the peptidase using Suc-Ala-Ala-Leu-pNA as substrate yielded Km and Vmax values 0.9 mM and 4.3 microM/min/3.5 microg protein, respectively. Negative staining of the purified uterine metalloprotease demonstrated spherical particles made up of several subunits. The earlier work had indicated that the uterine fluid metalloendopeptidase adhered to the head region of the ejaculated spermatozoa. It is very likely that this peptidase may be involved in assisting the fertilization process.

Estrus stage-specific proteinase in uterine fluid of the rat

An estrus stage-specific proteinase of an estimated molecular weight of 600 kDa was detected in uterine luminal fluid of the rat. Estradiol administrated sc to adult female ovariectomized and immature rats induced its production. The 600 kDa protein was stable to sodium dodecyl sulfate polyacrylamide electrophoresis under reducing conditions, and retained its proteolytic activity. The proteolytic activity was not inhibited by the following proteinase inhibitors: 1,10-phenanthroline, leupeptin, phenylmethylsulfonyl fluoride and pepstatin A. The 600 kDa proteinase was not detected in the uterus or in the spent medium in which uteri obtained from estrus stage of normal cycling rats or from estradiol-treated adult ovariectomized rats were cultured. Its presence in the uterine fluid suggests possible involvement in the fertilization process, viability of zygotes and/or implantation of blastocysts.

The effects of sequential administration of 17 beta-estradiol on the synthesis and secretion of specific proteins in the immature rat uterus

We report here results of a study of the effect of sequential administration of 1 microgram 17 beta-estradiol in vivo on the incorporation of L-[35S]methionine into specific proteins in vitro in the immature rat uterus. One-dimensional SDS-PAGE analysis of labeled secreted uterine proteins and cellular proteins extracted from the luminal epithelial and from the stroma plus myometrial uterine fractions revealed that estradiol preferentially stimulated the synthesis of 110 K, 74 K and 66 K secreted proteins, 180 K and 110 K epithelial proteins and a 175 K stroma-myometrial protein among others, while it decreased the relative rate of synthesis of a 32.5 K secreted protein and a 70 K stroma-myometrial protein. The 110 K protein, a secreted luminal epithelial protein whose labeling in vitro dramatically increased greater than 60-fold per mg endometrial DNA after in vivo estrogen stimulation, may be a useful marker for studying estrogen action in the luminal epithelium of the immature rat uterus. Comparison of the secreted proteins labeled at 28 h (4 h after a second injection) and at 54 h (6 h after a third injection) revealed that estradiol effected a sequential change in the pattern of synthesis of secreted uterine proteins in vitro. Comparison of the number and magnitude of changes in the synthesis of specific proteins in the luminal epithelium and the stroma plus myometrium revealed that protein synthesis in the luminal epithelium is clearly more responsive to estradiol and readily distinguishable from the responsiveness of the stroma plus myometrium.

Proteins synthesized in medial hypothalamus and transported to midbrain in estrogen-treated female rats

Results on the anatomy of ventromedial hypothalamic outputs, together with the temporal aspects of electrophysiological studies, predict that for reproductive behavior control sex steroids alter hypothalamic protein synthesis and transport of proteins to the dorsal midbrain. We have studied labeled proteins arriving in the dorsal midbrain after local microinjection of tritiated amino acids to the ventromedial hypothalamus. Estrogen treated and control ovariectomized female rats are significantly different in this respect, and in particular some proteins appear to be synthesized or transported in greater amounts in the estrogen treated animals. Physical characterization of these proteins and comparisons under a variety of endocrine conditions will suggest whether their synthesis could be part of the mechanism by which ovarian steroids affect behavior.