Glucose kinetics in normal, fasting, and insulin-treated cows

¹ Department of Animal Biology, School of Veterinary Medicine University of Pennsylvania, Philadelphia, Pennsylvania

Plasma glucose concentration in four cows averaged 58 mg/100 ml. It fell to 48 mg/100 ml during fasting, and to 29 mg/100 ml when long-acting insulin was given daily. From 45 until 150 min after a single injection of glucose-C¹⁴ the curves for plasma glucose specific activity plotted logarithmically against time approximated straight lines. The line during fasting lay above the normal line, while the line during insulin treatment fell below it. This suggests that there are two types of hypoglycemia, distinguished by different changes in the glucose pool. Characteristics of the pool sampled as plasma glucose were calculated from the slope and intercept of the lines from 45 to 150 min after injection. During fasting, the amount of exchangeable glucose fell to two-thirds and the glucose entry rate to half normal. This suggests that hypoglycemia develops during fasting because glucose utilization (outflow) exceeds glucose formation (inflow) with a decrease in the amount of glucose. In contrast, during insulin administration, the amount of exchangeable glucose was greater than normal, the entry rate was increased by one-third, and the apparent volume of glucose distribution was increased to 64% of the body weight. This suggests that insulin-induced hypoglycemia is due to an increase in the glucose "space" associated with the accumulation of exchangeable glucose inside some cells.

Key Words: insulin hypoglycemia • fasting hypoglycemia

Submitted on January 17, 1963