EXPRESSION OF VIGILIN IN THE UTERUS OF OVARIECTOMIZED STEROID-TREATEDRATS AND DURING THE ESTROUS-CYCLE

The expression of vigilin in the uterus of rats was investigated by im munoblotting and immunohistochemistry and compared to the ultrastructu ral features of the endometrial cells. Vigilin could not be detected i n the uteri of ovariectomized rats. Administration of estrogen, alone or in combination with progesterone, significantly stimulated the expr ession of vigilin, mainly in the luminal and glandular epithelial cell s. Ultrastructurally, these cells show the morphological features of a n increased protein synthesis. Untreated mature rats demonstrate a cyc lic pattern of vigilin expression with high levels during the estrogen -dominated proestrus and early estrus stages and low levels at metestr us. The down-regulation of vigilin starts with the occurrence of apopt osis and autophagocytosis in the epithelium, but precedes the vanishin g of the secretory granules. At diestrus the vigilin expression is int ermediate and the vigilin staining of the epithelial cells is reduced. However, the endometrial fibroblasts show a faint staining. Morpholog ically, these fibroblasts are characterized by large euchromatic nucle i and dilated cisternae of the rough endoplasmic reticulum. The result s suggest that in the uterus of rats the expression of vigilin is stim ulated by estrogen. Under the experimental conditions chosen no influe nce of progesterone on vigilin expression was detected.