Changes in distribution of lipid, glucose‐6‐phosphate dehydrogenase and malate enzyme within the liver lobule of the rat during adaptive hyperlipogenesis

Feeding rats a high‐sucrose, fat‐free diet after two days of starvation resulted in an initial accumulation of hepatic lipid and an increased activity of those enzymes which catalyze and support the formation of fatty acids from acetyl precursors. Rats starved for 48 hours were refed a high‐carbohydrate, fat‐free diet for 1, 2, 3, 5, 7 and 14 days. Frozen sections of liver were stained with Oil Red O for lipids. In adjacent sections glucose‐6‐phosphate dehydrogenase (GDH)and malate enzyme (ME) were localized and the relative enzyme activity evaluated. Enlargement and yellowing of the liver were noted after two to three days feeding of the fat‐free diet, but subsequently the liver appeared normal. Oil Red O staining demonstrated a progressive accumulation of lipid from the periportal to the centrilobular area during the first three days of refeeding. After the seventh day on the fat‐free diet, however, the lipid accumulation was less and the distribution appeared similar to that of animals maintained on a balanced diet. A marked increase in both GDH and ME activity was noted throughout the liver lobule after two days on the fat‐free diet. Enzyme activity remained high throughout the lobule during the balance of the experimental period, with maximum activity in the centrilobular area.