Effects of marine oil diet on peroxisomes and mitochondria of rat liver. A combined biochemical and morphometric study.

Feeding male rats a high cal% partially hydrogenated marine oil diet induced a response in the parenchymal liver cells at the cellular as well as the subcellular level. An adaptation in the lipid metabolism is indicated by an accumulation of triglycerides and a hypertrophy of the liver cells, and a rather selective increase (4.9-fold) in the specific activity of peroxisomal beta-oxidation. In addition, a slight proliferation of peroxisomes was observed; the volume fraction and the total number of peroxisomes increased 1.5-fold. The peroxisomes, however, preserved the biochemical and morphological homogeneity characteristic of peroxisomes in normal controls. At the mitochondrial level, a gradual development of megamitochondria was observed as the principal morphological change, with a 1.6-fold increase in the average size. The functional significance of this change remains to be determined. The effects of a partially hydrogenated marine oil diet on parenchymal liver cells appears to be manifestations with multiple causal factors. The high content of very long-chain trans fatty acids is of particular significance for the peroxisomal changes. An essential fatty acid deficiency, enforced by the presence of trans fatty acids in the diet, is most likely the determining factor for the development of megamitochondria.