Inhibition of rat hepatic aryl sulphotransferase IV by dihydrodiol derivatives of benzo[a]pyrene and naphthalene

Abstract

1. Although neither the (+)- nor (-)-enantioner of trans-benzo[a]pyrene-7,8-dihydrodiol was a substrate for aryl sulphotransferase IV from rat liver, both enantiomers inhibited the enzyme-catalysed sulphation of 1-naphthalenemethanol with K_i values of 3.7 ± 0.4 μM for the (+)-enantiomer, and 4.4 ± 0.3 μM for the (-)-enantiomer.

2. Based on the magnitude of the K_i values, the binding affinity of these dihydrodiols for the aryl sulphotransferase was significantly greater than that for the corresponding phenolic derivatives of benzo[a]pyrene. That is 7-hydroxybenzo[a]pyrene and 8-hydroxybenzo[a]pyrene were both substrates for aryl sulphotransferase IV, with apparent K_m values of 280 ± 41 μM and 370 ± 72 μM, respectively.

3. Both (+)- and (-)-trans-naphthalene-1,2-dihydrodiols were also inhibitors of aryl sulphotransferase IV, but with higher K_i values than would be expected from previously determined apparent K_m and K_i values for (R)-(-)- and (S)-(+)-1,2,3,4-tetrahydro-1-naphthols, respectively.