Dietary Response of Two Genetically Different Lines of Inbred Rats

Abstract

Summary

Responses of two inbred lines of rats to a stock diet or to diets (all low-fat, low-cholesterol) containing one of two levels of defatted egg or lactalbumin as the source of protein differed depending upon the genetic characteristics of the rats. One line with serum cholesterol levels in the range usually considered normal for the parent (BHE) stock of the same age showed no significant changes in levels with diet. The other line, with abnormally high levels, had levels above “normal” regardless of diet; yet an additional rise was seen in these rats when the protein was increased from 24% to 47%. The elevated serum cholesterol of this “high” line was accompanied by approximately the same amount of cholesterol in the livers and a smaller concentration of lipid than in the “normal” line. The “high” line was particularly susceptible to nephrosis and/or abnormal lipid metabolism. Although the defective control mechanism is not yet identified, it clearly is related to the partition of cholesterol between serum and liver and the error is heritable.