Abstract
Of glycogen storage diseases in man 10 types have been described. The enzyme defect has been identified in most of these. The condition appears to be rare in domestic and laboratory animals, although muscle glycogen storage disease, associated with phosphorylase kinase deficiency has been described in a strain of mice. Recently, excessive amounts of glycogen were found in the livers of inbred rats derived from the NZR/Gd strain. This sub-strain had extended to only 3 generations when the disease was discovered; its prevalence in the parent strain has not yet been determined. Whereas in unaffected rats glycogen virtually disappeared from the liver after 24 hr of fasting, the affected rats retained most, if not all, of their glycogen. This persisted even after 48 hr, of starvation. The activities of glucose-6-phosphatase and debranching enzyme were normal, whereas, as regards the phosphorylases, both total (a + b) and the active (a) activities were lower in the affected rats. Microscopically, glycogen was distributed throughout the liver cell cytoplasm and did not appear to accumulate in any organelle. Sections of muscle, kidney and heart from affected rats did not show excess glycogen.