A STUDY OF INSULIN METABOLISM IN AN INSULIN TOLERANT STRAIN OF MICE

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Abstract
The mechanism which gives the KL strain of mice high insulin tolerance was studied. Reaction to the administration of insulin was normal. Diaphragms of KL and Lt control mice did not differ in their ability to consume glucose and synthesize glycogen either with or without the stimulus of insulin in vitro. Injection of insulin produced a fall in blood glucose and a rise in muscle glycogen. The two strains seemed to differ in rate of recovery from changes in carbohydrate levels. No insulin was detected in the urine either strain after massive injection of the hormone. The difference between the 2 strains was apparently the presence of insulinase in the liver of the insulin tolerant mouse. This enzyme possessed an in vitro activity great enough to inactivate 200-300 units of insulin. It was present only in the liver cells. Fasting drastically lowered the demonstrable activity of this enzyme and also the tolerance of the KL animals to exogenous insulin. The thermal inactivation point of insulinase was between 70 and 80[degree]C.