Regulation of cellular retinoic acid binding protein expression in rhino mouse skin by all-trans-retinoic acid.

Cellular retinoic acid binding proteins (CRABP) are cytoplasmic proteins that bind all-trans-retinoic acid (RA) and other retinoids. The purpose of these studies was to determine the effects of topically applied RA on CRABP expression in rhino mouse skin. CRABP-II mRNA was significantly induced (3- to 4.5-fold) by a single dose of RA at 6 and 16 h after RA treatment, with a return to control levels at 48 h. CRABP-II message was not significantly elevated by 3 or 4 consecutive days of RA treatment, when assessed 24 h after the last treatment. CRABP-I mRNA was undetectable in control and RA-treated skin. We used radiolabelled RA binding combined with non-denaturing PAGE blot autoradiography to distinguish the CRABP subtypes. By this protein assay method, increases in CRABP-II were detected 24 and 48 h after a single application of RA, as well as after 3 and 4 days of RA treatment. RA treatment did not alter CRABP-I expression relative to the vehicle control. These results demonstrate that in mouse skin CRABP-II, but not CRAB-I, is inducible by RA, and is similar to how RA regulates CRABP in human skin.