Variable expression of cellular retinol- and cellular retinoic acid-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-binding protein (CRBP) and both types of cellular retinoic acid-binding protein (CRABP and CRABP II). Northern and Western blot analysis of the uteri revealed a peak of CRBP during diestrus and a peak of CRABP during proestrus, whereas CRABP II peaked sharply during estrus. Immunohistochemical studies showed CRABP II localized to the luminal epithelium, while both CRBP and CRABP were observed only in the smooth muscle layers of the uterus. In the ovary, CRABP was not detected, while CRBP levels remained relatively constant throughout the cycle and CRABP II peaked slightly during metestrus. CRBP in the ovary was localized to the oocytes, nearby granulosa cells, and some regions of stroma. CRABP II was found predominantly in the granulosa cells of mature follicles and early corpora lutea, as well as some regions of the stroma. These results suggest a need for further studies to assess the role of retinol and its metabolites in normal uterine function and ovarian follicular development.