Relationships between Plasma cAMP Concentration, cAMP Content in Various Tissues and Urinary cAMP Excretion in Streptozotocin-induced Diabetic Rats

Abstract

Relationships between plasma cAMP concentration, cAMP content in various tissues and urinary cAMP excretion were investigated to elucidate cAMP metabolism in streptzotocin-induced diabetic rats. The rats were made diabetic by a single injection of 60mg/kg of streptozotocin into the cervical vein. The plasma cAMP in various blood vessels and cAMP content in various tissues were measured 10 days after the injection of streptozotocin. Urinary cAMP excretion levels were determined 5 days before to 10 days after the streptozotocin injection.The increase in plasma glucose and IRG and the decrease in plasma IRI were certified in diabetic rats. The plasma cAMP concentration in the cervical vein and abdominal aorta in diabetic rats did not change significantly although their plasma cAMP concentration in the hepatic vein was significantly increased compared with the control rats. Hepatic cAMP content in diabetic rats was higher than that in the control rats, but the cAMP content in the renal cortex in the diabetic rats was significantly lower than that in the control rats. In the diabetic rats, the cAMP content in the brain, myocardium, small intestine and skeletal muscle was not different from that in the control rats.The urinary cAMP excretion level in the diabetic rats was significantly higher than that in the control rats from the second day to the 10th day after the injection of streptozotocin. The creatinine clearance as well as the cAMP clearance in the diabetic rats was higher than that in the control rats.In conclusion, in streptozotocin-induced diabetic rats, the plasma cAMP concentration did not increase after the injection of streptozotocin, despite an increase in cAMP content in the liver and plasma cAMP level in the hepatic vein. The increase in urinary cAMP excretion level in the diabetic rats as a result of increased glomerular filtration may be one reason for the failure of plasma cAMP to increase.