Effect of Age and Fasting on Glycogen Content of Liver and Muscle of Rats and Puppies

Previous studies (l-3) have shown that the metabolism of carbohydrates and ketone bodies in infants and children has distinct peculiarities which are characteristic of these age groups. The two most important differences between the young and the adult human being are (a) the ease with which hypoglycemia develops in infants and children when carbohydrates are withheld from the diet (1) and (b) the pronounced disposition to ketosis at certain ages. Studies (3) made on ketosis showed that under the influence of a ketogenic diet with a ratio of 2.5:1 ketonuria remains minimal in infants up to the age of 7 or 8 months. From then on, ketonuria develops with increasing ease during the first 4 years of postnat,al life, reaches a broad peak at from 4 to 8 years, and decreases during prepuberty, at which time it, equals values obtained in adults, values which are still much higher than those found in infants. To understand these findings, one should know more about the effect of age and fasting on t,he content of glycogen in liver and muscle. The reports of systematic studies thus far made in this field rarely include determinations in animal or human infants, although the period of infancy is obviously of the greatest interest to the problem. Because Collip and his collaborators (4) described a disposition to ketosis in rats in regard to age that was similar to that which was found (3) in human beings, rats were chosen for the experimental animals. Results of the experiments now reported show, however, some