| Popis: |
Purified cellular retinol-binding protein (cRBP) and cellular retinoic acid-binding protein (cRABP) mediated the transfer of their respective 3 H-ligands to nuclei and microsomes of retinol-sufficient rat testes interstitial cells in a saturable and reversible manner. Crossover experiments utilizing [ 3 H]retinol·cRBP/retinoic acid·cRABP and [ 3 H]retinoic acid·cRABP/retinol·cRBP did not result in dissociation of the labeled ligand from either the nuclear or microsomal fraction. Further, binding of free [ 3 H]retinol or [ 3 H]retinoic acid was not saturable nor was binding detectably reduced in the presence of unlabeled retinoids. When nuclei and microsomes were prepared from retinol-deficient tissues, cRBP-mediated binding of [ 3 H]retinol was also saturable and reversible. However, total binding was significantly increased in both cell fractions. Similarly, cRABP-mediated binding of [ 3 H]retinoic acid was significantly higher in retinol-deficient nuclei and microsomes. Extraction of cRBP- or cRABP-mediated nuclear-bound 3 H-retinoids with NaCl indicated that 50% of the retinol and retinoic acid were removed with 0.14 M NaCl. Retinol binding in nuclear subfractions including the 0.14 M NaCl fraction was pronasesensitive, RNase and DNase insensitive; retinoic acid was pronase- and RNase-sensitive, and DNase-insensitive. Nuclear binding of free retinoids was |
