Comparative Effect of Glucose Feeding on the Activities of Some Liver and Heart Enzymes in Rats

Abstract

Four enzymes involved in carbohydrate metabolism, as well as glutamic aspartic transaminase, and tissue glycogen were compared in livers and hearts of rats fed 60% glucose diets for 3, 7 and 14 days. These same activities were determined in control hearts, and isolated hearts perfused with 300 mg/100 ml glucose for 30 minutes. Whereas liver glycogen increased almost 40-fold by 7 days of diet, no significant change was found in heart glycogen. Heart glycogen decreased 24% during the preparation and preperfusion with Krebs buffer and continued to decrease during perfusion with 300 mg/100 ml glucose. Glucose feeding caused a marked rise in liver glucose-6-phosphate dehydrogenase which reached a peak at 3 days and thereafter declined slowly. No similar effect was noted in the heart enzyme which was initially one-third the level of that in liver. However, perfusion of isolated heart with glucose resulted in a significant decrease in glucose 6-phosphate dehydrogenase specific activity. Glucose feeding, or perfusion through heart, had little effect on the other measured liver or heart enzymes, except for heart glutamic-aspartic transaminase which initially declined during the first 7 days of diet and subsequently increased markedly.