Effects of n-3 and n-6 polyunsaturated fatty acid-enriched diets on lipid metabolism in periportal and pericentral compartments of female rat liver lobules and the consequences for cell proliferation after partial hepatectomy.

The effects of a low fat diet or diets enriched with either n-6 or n-3 polyunsaturated fatty acids (safflower or fish oil, respectively) on lipid metabolism in periportal and pericentral zones of female rat liver lobules were investigated in relation with cell proliferation after partial hepatectomy. It was found that cell proliferation was localized almost exclusively in periportal and midzonal areas and was significantly reduced by 60% after a fish oil diet only. The fish oil diet caused a strongly increased beta-oxidation capacity in peroxisomes and a moderately increased catalase activity. Catalase activity was mainly localized pericentrally, particularly after partial hepatectomy, whereas the capacity of lipid peroxidation product formation was doubled only in periportal zones in rats on a fish oil diet. The capacity of glucose-6-phosphate dehydrogenase activity to produce NADPH was distinctly lower in both zones of liver lobules as a result of the fish oil diet. Localization patterns and activity in liver lobules of NADPH-cytochrome c (P450) reductase were not significantly affected by fish oil diet. Therefore, it is concluded that elevated peroxisomal beta-oxidation and increased lipid peroxidation capacity in periportal zones of liver lobules coincide with reduced cell proliferation in hepatectomized rats on fish oil diet. These findings support the hypothesis that lipid peroxidation products are involved in the regulation of cell proliferation.