The effect of temperature on intracellular transport of asialo-glycoproteins in rainbow trout liver

The intracellular pathway of a endocytosed glycoprotein has been studied in rainbow trout (Oncorhynchus mykiss) liver by means of differential and isopycnic gradient centrifugation. When 125I‐tyramine‐cellobiose‐labelled asialoorosomucoid was injected intravenously, the protein was removed rapidly from the blood by hepatic endocytosis. The tracer was localized initially in a small, slowly sedimenting organelle (endosome) and transferred to the denser lysosomes where degradation took place. This process took several hours at the acclimated temperature of 10 ° C. The transport could be accelerated markedly or retarded by transfer of fish to higher or lower temperatures respectively. The intracellular transport steps were more susceptible to changing temperature than the internalization process. In particular, the degradation was temperature sensitive. These results may have implications for the effects of changing temperature on immune function in fishes. The impairment of transport upon a rapid temperature decrease, will reduce the rate of antigen processing and presentation in these animals.