IMPAIRMENT OF INDUCTION OF GLYCOLYTIC ENZYMES AND DEVELOPMENT OF INSULIN RESISTANCE IN RATS AS A RESULT OF CONTINUOUS INSULIN TREATMENT
ABSTRACT It has been established that the administration of insulin to rats for 10 days results in a considerable increase of RNA synthesis as well as in the activity of hexokinase and pyruvate kinase in liver cells. Electron microscopic studies have shown that on the 6th day of insulin treatment the size of hepatocytes nucleoli and the number of free ribosomes increase. Moreover on the 10th day of treatment the glycogen content is changed in the liver cells. Following long-term insulin treatment (16–20 days) the liver cells lose their capacity to respond by enhanced RNA synthesis and by the induction of hexokinase and pyruvate kinase. It has also been demonstrated that insulin administration for 10–15 days significantly decreases blood sugar. However, continuous insulin treatment (up to 25-27 days) elevates blood sugar to values surpassing even the normal value on day 27 of treatment. The administration of insulin to rats for 25–27 days leads to a decreased tolerance to glucose load. The content of immunoreactive insulin in the blood plasma increases considerably on day 10 of insulin injection and continues to rise more sharply on subsequent days of treatment.