MEAL-INDUCED CHANGES IN HEPATIC GLYCOGEN OF FASTED RATS

Hepatic metabolism of glucose and other nutrients influences feeding b ehavior. The present study was conducted to confirm prandial decreases in hepatic glycogen concentrations following a short-term fast. Male Sprague-Dawley rats were fasted 6-12 h during the Light phase before h aving access to chow for one or two 20-min meals at the beginning of t he dark phase. Plasma glucose and insulin concentrations in hepatic an d portal venous blood and hepatic glycogen concentrations prior to and at the end of each meal were compared. Glucose concentration in the h epatic vein was greater than that in the portal vein prior to the meal s but not at the end of the meal. Insulin levels were higher in the po rtal vein than the hepatic vein pre-and postprandially. Hepatic glycog en concentrations increased after each meal in younger (2-month-old) r ats but not older (6-month-old) rats. Fasting levels of hepatic glycog en were lower in the younger rats than the older rats; however, the in crease in hepatic glycogen was not due to differences in baseline glyc ogen concentrations at the start of the meal. The reported prandial de creases in hepatic glycogen of fasted rats were not apparent in this s tudy. Because of the difference between 2- and 6-month-old rats in per iprandial hepatic glycogen metabolism after a short-term fast, the age of the animal needs to be considered if the dynamics of liver glycoge n metabolism are to be incorporated into a model of food intake regula tion. (C) 1997 Elsevier Science Inc.