Acid and Alkaline Phosphatase Activity in the Liver of Brown and Rainbow Trout

Abstract

THE susceptibility of the rainbow trout to liver cell tumours following the administration of aflatoxin is well documented^1–3, as is the refractory behaviour of brown trout⁴. The different responses of these two closely related species probably indicate variations in basic metabolism. We decided to investigate histochemically some enzyme systems of the livers from brown, and rainbow trout. Although histologically these livers were similar, the activity and distribution of the acid and alkaline phosphatases showed distinct variations. The activity of alkaline phosphatase was greater in the brown than in the rainbow trout (Fig. 1a and b), while acid phosphatase was more active in the rainbow than in the brown trout (Fig. 1c and d). The distribution of the phosphatases varies throughout the fish kingdom^5,6, and the significance of the present findings is uncertain. The metabolic differences in these two species may begin to explain the inverse response to the induction of liver cell tumours. A significant loss of alkaline phosphatase from the livers of ducklings fed aflatoxin has already been reported⁷, as has the elevation of various serum enzyme concentrations, including alkaline phosphate, in the pig⁸. We are extending histochemical studies on the effect of aflatoxin at various doses on the two species of trout, and hope to elucidate the different effects, if any, on the enzyme systems in the livers with special reference to the phosphatases.