EFFECTS OF VITAMIN-A STATUS ON CELLULAR RETINOIC ACID-BINDING PROTEIN IN RAT SKIN AND TESTES

Cellular retinoic acid-binding protein levels were determined in the skin and testes of normal and retinol-deficient rats. All-trans [H-3]retinoic acid (1.1 TBq/mmol) was used to titrate the specific binding sites in tissue cytosol preparations. Scatchard plot analyses were used to determine the concentration of cellular retinoic acid-binding protein and its binding affinity (K(d)) for all-trans-retinoic acid. In normal rat skin the concentration of cellular retinoic acid-binding protein was 3317 +/- 924 (SD) fmol/mg protein and the K(d) was 1.98 +/- 1.0 x 10(-9) mol/l. In retinol-deficient rat skin the concentration of cellular retinoic acid-binding protein was 2584 +/- 1205 fmol/mg protein and the K(d) was 3.30 +/- 3.4 x 10(-9) mol/l. In the normal rat testes the concentration of cellular retinoic acid-binding protein was 2965 +/- 1187 fmol/mg protein and the K(d) was 2.30 +/- 2.1 x 10(-9) mol/l. In retinol-deficient rat testes the concentration of cellular retinoic acid-binding protein was 2439 +/- 383 fmol/mg protein and the K(d) was 0.3 +/- 0.2 x 10(-9) mol/l. These findings indicate that there are no significant differences in the levels of cellular retinoic acid-binding protein between normal and deficient rat skin and testes (p > 0.1, by Wilcoxon rank sum test). We therefore conclude that the level of cellular retinoic acid-binding protein in skin and testes may not be controled by the availability of vitamin A.