Cardiac Glycogen Content of Rats Alternately Fed High Protein-Diet and High Carbohydrate-Diet during Light and Dark Feeding Periods

Abstract

Wistar rats were maintained under the following ultradian lighting schedule (light/dark, 6 hr : 6 hr) : (1) group D, with lights on from 0300 to 0900 h and from 1500 to 2100 h; and (2) group L, reversal of the group D schedule, i.e., with lights on from 0900 to 1500 h and from 2100 to 0300 h. Both groups were alternately given a high protein diet (HPD) from 0900 to 1200 h and a high carbohydrate diet (HCHD) from 2100 to 2400 h every 12 hr. That is, food was given during dark periods of the light-dark cycle in group D and during light periods in group L. Other experimental conditions were rigidly standardized. After 4 weeks of feeding, the rats were decapitated at 0830, 1430, 2030 or 0230 h. In group D, ingestion of HPD decreased and HCHD increased cardiac glycogen. Similar changes were found with liver and skeletal muscle (gastrocnemius) glycogen and plasma glucose. A reciprocal relationship was found between changes in cardiac glycogen in group D and group L. The 24 hr overall mean of cardiac glycogen was significantly higher (P<0.001) in group D than in group L. Changes in liver glycogen and plasma glucose in group L were similar to those in group D. As plasma free fatty acids (FFA) concentrations were decreased by ingestion of diets in both groups, a positive correlation was not present between cardiac glycogen and plasma FFA concentrations. Cardiac glycogen was affected by lighting conditions, in addition to feeding and diet composition. These results suggested that abnormal lighting conditions act as a stress on animals. © 1985, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.