Chemical evidence for the presence of glycogen-like polysaccharide in the liver blood of diabetic animals

Abstract

Histological evidence for the presence in the hepatic capillaries of diabetic animals of material which stains by Best's carmine method in the same manner as the glycogen present in the liver cells (Huber and Macleod) has led us to investigate whether a polysaccharide could be separated by chemical means from the blood of the vena cava. In the first experiments of this nature (with G. E. Simpson), the blood of the vena cava was collected in excess of alcohol and the resulting precipitate treated with KOH in the usual manner. From the hydrolysis mixture a small amount of alcohol-precipitable material was secured, which after purification gave a violet color with iodine and exhibited reducing properties on hydrolysis. This material was sometimes isolated from the blood of normal animals (etherized), as well as from that of diabetic animals. In all cases, however, the yields were very small and uncertain, so that I have recently changed the method of isolation. Instead of precipitating with alcohol as the first step, the blood is now received directly into saturated alkali. On account of the high cost of KOH, a series of preliminary experiments were performed to see whether, after hydrolysis of the protein and heating with NaOH, a solution would be obtained from which the glycogen could be quantitatively precipitated by alcohol. After heating solutions consisting of equal volumes of a relatively pure glycogen solution and of saturated NaOH (purified by alcohol) on the boiling water bath for periods exceeding three hours, it was found that the glycogen could not be precipitated by the addition of an excess of alcohol, unless the solution was almost neutralized with HCl and therefore contained an excess of sodium chloride.