VARIABLE EXPRESSION OF CELLULAR RETINOL-BINDING AND CELLULAR RETINOICACID-BINDING PROTEINS IN THE RAT UTERUS AND OVARY DURING THE ESTROUS-CYCLE

Ovaries and uteri from normal adult female rats at known stages of the estrous cycle were analyzed for the presence of cellular retinol-bind ing protein (CRBP) and both types of cellular retinoic acid-binding pr otein (CRABP and CRABP II). Northern and Western blot analysis of the uteri revealed a peak of CRBP during diestrus and a peak of CRABP duri ng proestrus, whereas CRABP II peaked sharply during estrus. Immunohis tochemical studies showed CRABP II localized to the luminal epithelium , while both CRBP and CRABP were observed only in the smooth muscle la yers of the uterus. In the ovary, CRABP was not detected, while CRBP l evels remained relatively constant throughout the cycle and CRABP II p eaked slightly during metestrus. CRBP in the ovary was localized to th e oocytes, nearby granulosa cells, and some regions of stroma. CRABP I I was found predominantly in the granulosa cells of mature follicles a nd early corpora lutea, as well as some regions of the stroma. These r esults suggest a need for further studies to assess the role of retino l and its metabolites in normal uterine function and ovarian follicula r development.