Hepatic systems, trout

Schwen, R.J. and G.J. Mannering. 1982a. Hepatic cytochrome P-450-dependent monooxygenase systems of the trout, frog and snake. II. Monooxygenase activities. Comp. Biochem. Physiol. 71B 437-443. 

Stott, W.T. and Sinnhuber, R.O. Trout hepatic enzyme activation of aflatoxin-B] in a mutagen assay system and inhibitory effects of PCBs. Bull. Environ. Contam. Toxicol. (1978) 19, 35. 

The present study was undertaken to determine the influence of several levels of dietary casein upon the activities of trout hepatic enzyme systems which may be involved in the in vitro activation and detoxification of AFB. In addition, the effect of Technical Paper No. 4883, Oregon Agricultural Experiment Station. 

The decrease in cytochrome P-450 content correlated with a lowering of trout AE activity observed in hepatic microsomes recovered from fish fed high levels of casein, versus those from fish fed low casein diets. As shown in Table III, up to a 32% decrease in the production of the epoxide dieldrin was noted. Similar results have been observed in 10 month old rainbow trout with a nearly identical maximum decrease (unpublished data). Since AFB activation has been shown to involve a cytochrome P-450 dependent enzyme system (19, 20, 22) and trout... 

The observed mutagenic responses to AFB reflect the overall effects of activation and detoxification systems on the in vitro metabolism of AFB. It appeared that the effect of high casein levels fed to trout was that a greater amount of activated AFB was produced and/or that less could be detoxified by these fish than by those fed lower casein diets. If lowered cytochrome P-450 content and AE activities in fish fed the high casein diets represented a decrease in the activation of AFB, then these effects were overcome by the observed decreases in GTr activity and/or increases in AFB conversion to AFL relative to those of trout fed lower casein diets. Alternately, the results could be explained by dietary effects upon some unknown OAFB metabolizing enzyme system in trout, upon free GSH levels in hepatic tissue, or that the levels of the cytochrome P-450 involved in AFB activation were not reflected by the observed total cytochrome P-450 levels. 

Enrofloxacin is mainly eliminated by hepatic metabolism, and systemic clearance of the drug varies between species. In sheep, horses, dogs and pigs the average clearance of enrofloxacin is in the range 5.75-8.56 mL/min kg, while enrofloxacin clearance (mL/min kg) differs more widely between other species rabbits (17.9), llamas (12.0), chickens (3.3), turkeys (8.9), houbara bustard (5.7) and fingerling rainbow trout (Oncorhynchus mykiss) at 15°C (1.25). Systemic clearance of enrofloxacin represents mainly hepatic clearance composed of a variety of metabolic pathways, which include N-deethylation to ciprofloxacin. 

Roch, M., J.A. McCarter, A.T. Matheson, MJ.R. Clark and R.W. Olafson. Hepatic metallothionein in rainbow trout (Salmo gairdneri) as an indicator of metal pollution in the Campbell river system. Can. J. Fish. Aquat. Sci. 39 1596-1601, 1982. 

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