Abstract
The effect of threonine on growth and plasma cholesterol levels were studied in Donryu and Sprague-Dawley rats fed on a rice diet containing cholic acid or both cholic acid and cholesterol. The addition of cholic acid only or both cholic acid and cholesterol to the rice diet produced a body weight decrease in Donryu rats, being especially significant for the diet containing cholic acid only. However, the body weight decrease was partly moderated by addition of threonine to the rice diet supplemented with cholic acid. No differences were observed in the growth of Sprague-Dawley rats fed on the rice diet containing cholic acid, cholesterol or threonine compared with the control group fed on the diet without such additives. When both Donryu and Sprague-Dawley rats were fed the rice diet containing cholic acid, the plasma threonine concentration was significantly reduced in Donryu rats, whereas no such change was observed in Sprague-Dawley rats. When threonine was added to the rice diet containing cholic acid, an elevated plasma threonine concentration was observed in both groups, being especially significant in Sprague-Dawley rats. The plasma and liver cholesterol levels were increased in both rat strains compared with the control group when threonine was added to the rice diet containing cholic acid and cholesterol. Addition of serine or glycine to the diet containing cholic acid and cholesterol had little effect on either growth or the plasma cholesterol level of Donryu rats, although it induced a higher level of HDL-cholesterol in plasma.
