Disubstituted diaryl diselenides inhibit delta-ALA-D and Na+, K+-ATPase activities in rat brain homogenates in vitro.

Toxicological and pharmacological studies demonstrated that the introduction of functional groups into the aromatic ring of diphenyl diselenide alter its effect. The aim of this study was to evaluate the in vitro effect of m-trifluoromethyl-diphenyl diselenide (m-CF(3)-C(6)H(4)Se)(2), p-chloro-diphenyl diselenide (p-Cl-C(6)H(4)Se)(2) and p-methoxyl-diphenyl diselenide (p-CH(3)O-C(6)H(4)Se)(2) on delta-aminolevulinate dehydratase (delta-ALA-D) and Na(+), K(+)-ATPase activities in rat brain homogenates. Diselenides inhibited delta-ALA-D activity (IC(50) 4-6 microM [concentration inhibiting 50%]), and dithiothreitol (DTT) restored the enzyme activity. ZnCl(2) (100 microM) did not restore delta-ALA-D inhibition caused by (p-Cl-C(6)H(4)Se)(2) and (m-CF(3)-C(6)H(4)Se)(2). Na(+), K(+)-ATPase activity was more sensitive to (p-Cl-C(6)H(4)Se)(2) and (m-CF(3)-C(6)H(4)Se)(2) (IC(50) 6 microM) than (p-CH(3)O-C(6)H(4)Se)(2) and (PhSe)(2) (IC(50) 45 and 31 microM, respectively). DTT restored the activity of Na(+), K(+)-ATPase inhibited by diselenides. The effect of diselenides on Na(+)/K(+)-ATPase is dependent on their substitutions in the aromatic ring. The mechanism through which diselenides inhibit delta-ALA-D and Na(+), K(+)-ATPase activities involves the oxidation of thiol groups.