A comparison of direct enzymatic determination of glycogen in liver and heart

Abstract

Several enzymatic methods for the measurement of glycogen have been developed including degradation by diazyme (1) or amylo-α-1,4-α-1,6-glucosidase (2–6) followed by determination of glucose with glucose oxidase (1–3,6) or hexokinase and glucose-6-P- dehydrogenase (4,5). Bueding and Hawkins (7) developed a method for the microdetermination of glycogen using phosphorylase and amylo-α-1,4-α-1,6-glucosidase which was later modified so that commercially available enzymes: phosphrylase a, P- glucomutase, and glucose-6-P-dehydrogenase could be used (8). In determining the glycogen content of tissue samples, homogenization in perchloric acid (4,5) or heating tissue in 0.03 n HCl (9) have been included prior to theenzymatic analysis. Yet, it has also been reported that glycogen can be deermined directly in very dilute homogenates of liver or muscle in water (3). Likewise, direct enzymatic procedure for the detemrination of glycogen in homogenates of liver in water by degrading glycogen to glucose by treament with amylo-α-1,4-α-1,6-glucosidase has yielded higher values for glycogen content than those for tissue digestion with KOH, precipitation of glycogen with ethanol, and finally acid hydrolysis (6). In the present report, the feasibility direct enzymatic determination of glycogen in homogenates of liver with amylo-α-1,4-α-1,6-glucosidase has been reaffirmed. However, glycogen content of heart tissue determined by the same enzymatic procedure directly in homogenates in water was substantially lower than that obtained by extraction with KOH, glycogen precipitation with ethanol, and then enzymatic analysis.