Metabolic Adaptations in Higher Animals. 10. Glutamic Dehydrogenase Activity of Rats Consuming High Protein Diets.

Abstract

Summary The activity of glutamic de-hydrogenase (GDH) has been determined in the tissues of rats consuming normal or high protein diets. In rats consuming a stock diet the distribution of GDH activity was as follows in order of decreasing activity: liver, kidney, intestinal mucosa, intestinal serosa, spleen, heart, diaphragm, and gastrocnemius muscle. Rats adapted to an 80% casein diet for 7-14 days had a higher activity per g of tissue in liver and kidney but not in spleen, heart or gastrocnemius muscle. Compared with rats consuming a 25% casein diet the activity of rats placed on an 80% casein diet rose 15% per g of liver, the same as the liver protein concentration, and 32% per g of body weight. Pair-fed rats had a higher activity per g of liver but no change per g of body weight. The increase in kidney GDH reached a maximum of 35% per g of tissue (85% per g of body weight) 4 days after changing the dietary casein level from 25 to 80%. The activity was proportional to the casein content of the diet for groups receiving more than 18% of casein. The activity of the kidney was not significantly affected by feeding a low carbohydrate-high fat diet or by substituting various dispensable amino acids for the glutamic acid in an amino acid diet.