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

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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