Studies on the relationships between insulin, glucosamine, and glucose in rat diaphragms.

One approach toward the elucidation of the mechanism of insulin action is to study the effect of insulin on glucose analogues. Studies of this type have been carried out in this laboratory by use of the eviscerated and nephrectomized rabbit. It has been shown (l), with the above test preparation, that insulin accelerates the transfer of n-glucosamine from the extracellular fluid into the cells. Concurrently, the demand for glucose by the maximally insulin-treated animal was lowered considerably after a single injection of n-glucosamine. Since the decrease in glucose requirements of these animals could not be explained, even assuming complete conversion of n-glucosamine to glucose, it was suggested that n-glucosamine acts in some manner as a metabolic block. While the metabolic changes observed in the eviscerated animal are usually attributed to the muscle cells, it is desirable to test this directly. Consequently, we have examined the effect of insulin action on glucosamine, using the isolated rat diaphragm. Studies of this type can be carried out in the absence of glucose, in contrast to the intact animal, in which glucose is always available to the muscle tissues.