The influence of dietary carbohydrate and fat on kidney calcification and the urinary excretion ofN-acetyl-β-glucosaminidase (EC3.2.1.30)

Abstract

1. Male Sprague-Dawley rats were fed on diets containing either sucrose or starch as the carbohydrate component. In one experiment, the diets also contained 200 g either butter or polyunsaturated margarine/kg; in a second experiment, the diets contained less fat in the form of 20 g maize oil/kg.2. Over a period of 11 months assays were made in the urine of several ions and of the activity of the enzymeN-acetyl-β-glucosaminidase (β-2-acetamido-2-deoxy-β-D glucoside acetamidodeoxygluco-hydrolase;EC3.2.1.30); at 13 months, examination was made of some of the abdominal viscera, especially of the kidneys.3. In rats fed on the higher amount of fat, dietary sucrose produced a higher activity of the enzyme than did dietary starch, and a greater excretion of inorganic phosphate.4. With both the higher and lower amounts of dietary fat, sucrose led to an increase in the weight of the liver and of the kidneys, and an increase in the concentration of calcium and of phosphate in kidney tissue. With the higher amount of fat, sucrose also produced an increase in the concentration of magnesium in the kidney. There was no difference in the concentration of any of the ions assayed in the plasma or, apart from inorganic phosphate, in the urine.5. The kidneys of the sucrose-fed rats showed nephrocalcinosis, mostly in the cortico-medullary region, and basophilic deposits in the tubules. Attention is drawn to this unusual occurrence of nephrocalcinosis in male rats.