The Effects of Diet, Partial Hepatectomy and Growth-Promoting Factors on the Composition of the Rat Liver

Abstract

The effect of normal diets (22% protein) and of low protein-high fat diets (9% protein) on the liver constituents of intact rats was studied. The liver lipids in intact rats on normal diets were lower when 30 mg of choline were added daily to the diet than on this diet without choline (0.76 gm % as compared to 2.55 gm %). In intact rats on the 9% protein diet the lipid content of the liver varied, averaging about 10 gm % after 22 days on the diet. The increase in liver lipids was associated with a decrease in the nitrogen content of the liver. After being maintained on the low protein-high fat diet for about 42 days, groups of rats were partially hepatectomized. When they were continued on this diet, the lipid content of the liver was further increased at the time of sacrifice, 6 to 15 days later. When the rats continued on the low protein-high fat diet after partial hepatectomy were given 5 μg of vitamin B12 by injection daily, there was a consistent decrease in the liver lipids and an increase in liver nitrogen at the time of sacrifice. The injection of liver extract was also associated with a decrease in the liver lipids, but not as consistent a decrease as that occurring with vitamin B12. Increasing the protein content of the diet to 16% following partial hepatectomy was associated with some lipotropic effect and an increase in the liver nitrogen, but this was not as uniform as when the protein in the diet was increased to 26%. Microscopic examination of the livers of the rats at the time of hepatectomy and at the time of sacrifice showed an increase in lipid deposition in the animals continued on the low protein diet, and not receiving any additional therapy. The administration of both liver extract and vitamin B12 was associated with microscopic evidence of regeneration of liver cells, more marked in the animals receiving vitamin B12. In the animals changed to the 26% protein diet, regeneration of the liver cells was present but to a less marked degree.