Dietary and hormonal regulation of pancreatic xanthine dehydrogenase in the chick.

Chick pancreatic xanthine dehydrogenase (PXDH) is synthesized in response to feeding. Its induction generally correlates with growth; in the absence of growth, induction is observed uniquely when pure glucose is fed. This study attempted to determine what events after feeding lead to PXDH synthesis. When chicks were fed diets providing equal numbers of calories/gram of diet and varying only in the major energy source (carbohydrate, protein, or fat), PXDH response was high in the carbohydrate-fed, low in the protein-fed, and minimal in the fat-fed chicks. A unique, transitory increase in plasma glucose occurred in the carbohydrate-fed chicks within day 2 after feeding. These unique effects of dietary glucose indicated that the induction of PXDH after feeding was linked to carbohydrate metabolism. Effects of injected insulin on PXDH were examined. Insulin doses between 0.001 and 10.0 IU induced PXDH 25-60% above the activity found in carbohydrate-fed chicks. The initiation of PXDH accumulation may be the result of a sequence of metabolic responses to dietary carbohydrate beginning with an increase in plasm glucose, which induces an insulin response.