Specific binding of dehydroepiandrosterone sulfate to rat liver cytosol: a possible association with peroxisomal enzyme induction.
Incubation of [3H]dehydroepiandrosterone sulfate (DHEAS) with rat liver cytosol demonstrated its specific binding with a dissociation constant of 72 +/- 14 nM and a maximal binding capacity of 312 +/- 105 fmol/mg cytosol protein. The binding correlated with the amount of cytosol protein, and depended on time, temperature and pH, with equilibrium being reached after 6 h at 0 degrees C and pH 7.5. Boiling or treatment of the cytosol with proteases or sulfhydryl-blocking reagents affected the binding. The apparent molecular mass of the binding entity was estimated to be 160-230 kDa by HPLC gel filtration. In competitive binding studies, free steroids, including dehydroepiandrosterone (DHEA), sulfatase substrates and ligands of organic anion binders such as ligandin and fatty acid binding protein, had no effect on the [3H]DHEAS binding. Peroxisome proliferators also had no effect, except Wy-14,643. Competition with various steroids related to DHEAS revealed strict structural requirements for DHEAS binding, in which epiandrosterone sulfate was almost as effective as unlabeled DHEAS in inhibiting [3H]DHEAS binding. These findings indicated the presence of a binding protein highly specific to DHEAS in rat liver cytosol. The DHEAS binding in liver cytosol was 2-fold higher in male than in female rats. The cytosolic DHEAS binding was highest in the liver, followed by the kidney and heart. The possibility of association between the DHEAS binding and DHEA induction of peroxisomal beta-oxidation is discussed.
Yamada
J
J
Department of Clinical Biochemistry, Tokyo College of Pharmacy, Japan.
Sugiyama
H
H
Sakuma
M
M
Suga
T
T
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives* / Q000378:metabolism; D019314:Dehydroepiandrosterone Sulfate; D004790:Enzyme Induction; D005260:Female; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012737:Sex Factors; D013696:Temperature; D013997:Time Factors
D003687:Dehydroepiandrosterone; D019314:Dehydroepiandrosterone Sulfate