[The effect of glucocorticoids on glucose metabolism in pygmy goats. 2. Glucose turnover and recycling].

In the present study glucose kinetic parameters like pool size, distribution volume and rates of total entry and irreversible loss were determined in four castrated male African pygmy goats during hyperglycemia induced by an intravenous glucocorticoid injection (0.25 mg dexamethasone = DXM per kg body weight). Experiments were done at two different metabolic states, "fed" once daily and "fasted" after three days of starvation. The use of [U-14C]- together with [2-3H]- or [6-3H]-glucose made it possible to show changes in rates of gluconeogenesis, phosphorylation and specific recycling of glucose-C (e.g. lactate/alanine). During glucocorticoid induced hyperglycemia (+45%) in fed animals de novo synthesis of glucose (+5%) and lactate/alanine recycling increased (+4%). Rates of irreversible loss for all applied tracers in fasted animals formed only two thirds of the values of fed animals. During hyperglycemia (+40%) after DXM-injection de novo synthesis of glucose (+8%) and lactate/alanine recycling also increased (+27%). Furthermore the rate of phosphorylation of glucose decreased in fasted pygmy goats. The increase in availability of glucose both in fed and fasted animals is due to an increase in gluconeogenesis. In fasted animals additionally a decrease in the rate of phosphorylation and therefore of the peripheral glucose turnover has to be considered.