Dietary protein and carbohydrate effects on the distribution of glycogen in chicken liver

Abstract

Fourteen-d-old Ross male broiler chickens were fed diets containing either 140 or 200 g crude protein and 12 KJ ME/kg diet at 16.7 J×d −1 × body weight in g 0.66 and diets containing either 200 or 280 g crude protein and 12 KJ ME/kg diet at 11.8 J×d −1 × body weight in g 0.66. Chickens were killed at 28 d of age and indices of liver glycogen metabolism were determined in soluble and particulate fractions (50,000×g supernatant and pellet, respectively) of liver. Glycogen synthase (EC 2.4.1.21) activity was assayed in the presence of 0 to 8 mM glucose-6-phosphate (G-6P). Glycogen phosphorylase (EC 2.4.1.1) activity was measured in the presence of 0 to 3.3 mM adenosine monophosphate. Glycogen was found in the particulate fraction while free glucose was found in the soluble fraction. Glycogen synthase activity was found in both fractions. Particulate activity was inversely related to particulate glycogen as was the apparent Ka for G-6P for activity in the 8,000×g supernatant. Glycogen phosphorylase activity was found only in the particulate fraction and was also inversely related to glycogen content. Differences in activity appear to relate to enzyme activation states. Food restriction regimens produce a meal-feeding-like response in liver glycogen metabolism. Dietary crude protein content did not alter liver glycogen metabolism.