title: Effects of temperature and dietary n-3 and n-6 fatty acids on endocytic processes in isolated rainbow trout (Oncorhynchus mykiss, Walbaum) hepatocytes.
abstract: Effects of different incubation temperatures (2, 8, 14 and 20°C) and hepatocyte membrane fatty acid composition on the rate of internalization and lysosomal degradation of the ligand, mannosylated albumin, that is taken up by receptor-mediated endocytosis, were investigated in rainbow trout (Oncorhynchus mykiss, Walbaum). The fish were kept at a water temperature ranging from 9 to 14°C and fed pelleted diets coated with either capelin oil (control), EPA/DHA-concentrate (rich in n-3 polyunsaturated fatty acids) or soybean oil (rich in n-6 unsaturated fatty acids) for at least 3 months prior to sampling. The endocytic uptake mediated by the mannose receptor was very efficient at all temperatures studied. Lysosomal degradation, on the other hand, came to a halt below 8°C. The activation energies for uptake and degradation were 54.6 and 164.2 kJ/mol respectively. No negative effects of increased amounts of either n-3 or n-6 fatty acids were observed on the endocytic parameters studied. On the contrary, multivariate analysis indicated a positive relationship between high levels of n-6 fatty acids and low unsaturation index in the phosphatidylcholine (PC) fraction of the hepatocytes and the internalization rate of 2°C, meaning that the rate of receptor-mediated endocytosis may be affected by membrane fatty acid composition.
authors.affiliation: AKVAFORSK, P.O. Box 5010, 1432 Ås, Norway.
authors.forename: C
authors.initials: C
authors.lastname: Røsjø
authors.forename: T
authors.initials: T
authors.lastname: Berg
authors.forename: K
authors.initials: K
authors.lastname: Manum
authors.forename: T
authors.initials: T
authors.lastname: Gjøen
authors.forename: S
authors.initials: S
authors.lastname: Magnusson
authors.forename: M S
authors.initials: MS
authors.lastname: Thomassen