INDUCIBLE EXPRESSION OF CELLULAR RETINOIC ACID-BINDING PROTEIN-II IN RAT OVARY - GONADOTROPIN REGULATION DURING LUTEAL DEVELOPMENT

Two members of the superfamily of small intracellular carrier proteins for lipophilic compounds are cellular retinoic acid-binding protein a nd cellular retinoic acid-binding protein II [CRABP(II)]. CRABP is fou nd in many adult tissues, whereas CRABP(II) is more restricted and is reported as abundant primarily in shin. Here we report a much greater expression of CRABP(II) in rat corpus luteum than in any other organ/t issue examined, including skin. A rat complementary DNA clone encoding CRABP(II) was isolated and the ovarian expression followed during gon adotropin induction of follicular development in the pseudopregnant ra t. The pattern of rat CRABP(II) messenger RNA and protein expression c orrelated with the appearance of corpora lutea and the rise in progest erone production as the corpora lutea developed, and was similar to th e induction of 3 beta-hydroxysteroid dehydrogenase. Immunohistochemica l localization revealed that CRABP(II) appeared in luteal cells and wa s dramatically restricted to their cytoplasmic compartment, with no ap parent presence in the nucleus. This suggests that CRABP(II) may be ex pressed to restrict retinoic acid from occupying nuclear retinoic acid receptors, implying that the differentiation and maintenance of the r at corpus luteum may involve in part a release of certain pathways fro m retinoid suppression.