Effects of the brominated phenol, lanosol, on cytochrome P-450 and glutathione transferase activities in Haliotis rufescens and Katharina tunicata.

The relationship between biochemical transformation mechanisms and dietary preferences has been little studied among marine herbivores. Here we report on basal activities and kinetic parameters of steroid hydroxylase and glutathione transferase from digestive gland tissue of the marine molluscan generalist herbivores Haliotis rufescens and Katharina tunicata and the differential effects of the brominated phenol lanosol [1,2-dihydroxy-3,4-dibromo-5-(hydroxymethyl)-benzene] on the activity of these enzymes. Lanosol and other brominated aromatic compounds are prevalent among filamentous red algae frequently consumed by K. tunicata and have been shown to deter feeding in species of Haliotis. Animals were gavaged daily with 10 mg of lanosol per kg of wet mass for 3 days. Mean basal levels of estradiol and testosterone hydroxylase and glutathione transferase specific activities were higher in digestive gland tissue from H. rufescens relative to that of K. tunicata, and only K. tunicata glutathione transferase specific activity was affected by lanosol treatment. Apparent enzyme kinetic parameters (K(m) and V) for the substrate estradiol were higher in K. tunicata, and glutathione transferase from H. rufescens showed a higher efficiency of turnover compared with glutathione transferase from K. tunicata based on V/K(m) ratios. These results suggest a potential relationship between detoxification enzyme induction mechanisms and feeding behaviors among marine herbivores.