Variation of Hepatic Ethoxycoumarin O-de-ethylase Activity with Body Weight and Other Factors in Brook Trout (Salvelinus fontinalis)

Abstract

Data from several previous experimental studies of hepatic mixed function oxidase (MFO) activity were reexamined to study the possible relationship between ethoxycoumarin O-de-ethylase activity and body weight and other factors in "uninduced" brook trout (Salvelinus fontinalis). Weight-specific O-de-ethylase activity was inversely related to body weight; regression of the log transformation of the total hepatic O-de-ethylase activity on log liver weight yielded a regression coefficient of 0.850 ± 0.047 close to the value of ~0.75 expected for a relationship based on overall metabolic rate. The regression coefficient was significantly higher in males than in females. Multiple regression analysis showed O-de-ethylase activity to be positively correlated with both microsomal protein and cytochrome P-450 content. The data confirm that size (or age) is a factor to be eliminated in any biological effects monitoring program based on MFO assays.Key words: mixed function oxidases, ethoxycoumarin O-de-ethylase, brook trout, Salvelinus fontinalis; hepatic mono-oxygenases