Factors within the body determining the glycogen reserves in the tissues of rats with transplantable tumours.

Attempts have been made to determine the reason for the depletion of glycogen reserves in tumour-bearing rats. The possible roles of anorexia, competition for glucose by the tumour, and lack of hormonal control of glycogen biosynthesis have been investigated. The glycogen content of the liver, skeletal muscle, and brain, and the levels of glucose and the hormones corticosterone, insulin, and glucagon were determined in healthy rats which had been starved for various periods and in tumour-bearing rats carrying the fast-growing Zajdela ascites hepatoma or the slow-growing solid hepatoma 27. It was found that towards the terminal stages of tumour development there was an increase in the content of corticosterone and glucagon in the blood serum and also an increase in the glycogen reserves in skeletal muscle and brain despite the presence of hypoglycaemia and hypo-insulinaemia. There was at this time a sharp fall in the level of liver glycogen. It is shown that neither anorexia nor excessive competition for glucose by the tumour were the main reasons for liver glycogen depletion and hypoglycaemia. A strong correlation was observed, however, between the occurrence of anaemia and the loss of liver glycogen, which suggests that the former may be an important factor in the changes in host tissue observed in response to tumour growth.