Changes in Perilymph Glucose Concentration: Occurrence in Hyperglycemia and Hypoglycemia

Glucose concentration in serum, cerebrospinal fluid (CSF), and perilymph before and after inducing hyperglycemic and hypoglycemic states was measured in the cat. The perilymph glucose concentration was about equal to CSF and approximately two thirds of the serum glucose concentration. Thirty minutes after glucose infusion the increase in glucose concentration in perilymph paralleled the increase in serum. However, after insulin infusion, perilymph glucose concentration did not drop as rapidly as it did in blood or CSF. The lower glucose concentration in perilymph found in initial samples compared to its concentration in initial samples of serum and also the delayed decrease in the concentration of glucose in perilymph after insulin infusion may indicate the existence of a mechanism that regulates the movement of glucose between labyrinthine fluids and blood.