Effect of adrenalectomy and hypophysectomy on responses of rat liver enzymes to high-fructose diets

Abstract

The effect of dietary fructose on the activities of a number of enzymes was studied in normal, adrenalectomized, and hypophysectomized male Sprague–Dawley rats. The effect of feeding a high-fructose diet on relative liver size, soluble protein, glycogen, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase, glyceraldehyde-3-phosphate dehydrogenase, and glucose-6-phosphatase was not appreciably altered by endocrinectomy. It appears, therefore, that the fructose effect on these rat liver constituents is not mediated by adrenal or pituitary hormones, although endocrine function may influence enzyme activity. The enzymes which were not particularly affected by either endocrinectomy are those associated with the metabolism of phosphorylated intermediates.The fructose diet increased the activities of L-α-glycerophosphate dehydrogenase and lactic dehydrogenase to a greater extent after endocrinectomy; therefore, an inhibition of the fructose effect in normal animals by endocrine function was postulated. The effect of feeding fructose on the activities of the pentose-phosphate-metabolizing enzymes and glutaminase was abolished by hypophysectomy. In this case it was postulated that pituitary function is required for the fructose effect as a permissive agent. The fructose-mediated increases of malic enzyme and uridine-diphosphoglucose dehydrogenase were diminished in magnitude after endocrine removal, but not abolished.The activities of the urea-cycle enzymes, transaminases, and serine dehydrase were not increased by fructose feeding. The relationship between the fructose effect and endocrinectomy appeared to be complicated in the case of malic dehydrogenase and fumarase.