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

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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.