NAD glycohydrolase activity in the liver of rats fed on excess leucine diet and low or high protein diet.

In rats fed for 2 weeks on a 10% casein diet supplemented with 5% leucine, the hepatic NAD content was lowered when comparing with the control rats pair-fed on the 10% casein diet. The hepatic NAD glycohydrolase [EC 3.2.2.5] activity increased by 25% in the leucine-supplemented diet-fed rats and by 40% in the nicotinic acid-free diet-fed rats. The hepatic NAD glycohydrolase activity in the rats fed on the nonprotein diet freely for 1 week was elevated by 60% compared to the rats fed on the 18% casein diet. The hepatic NAD content in the former animals was significantly lower than that in the latter. The 70% casein diet caused changes in neither hepatic NAD content nor NAD glycohydrolase activity. These results indicated an inverse relationship between hepatic NAD content and NAD glycohydrolase activity.