Insulin Resistance in Late Pregnant Rats / 영남의대학술지

The influence of normal late pregnancy on insulin action and insulin secretion was studied in the Sprague-Dawley female rats. On 20th day after mating, intravenous glucose tolerance test(IVGTI) was performed in non pregnant control and pregnant rats. As results of IVGTT, glucose disappearance rate was not significantly different in both groups, but secretory response of insulin was significantly(p<0.05) increased in pregnant rat. And the ratio of insulin/ .glucose was significantly higher in pregnant rats, which means existence of insulin resistance. These insulin resistance was overcomed by increased secretory response of pancreatic insulin. Insulinogenic index( A insulin/glucose - 5 min) was highly significantly (r=0.62, p<0.01) correlated with progesterone concentration. Glycogen level and amounts of "C-glucose incorporated into glycogen after IVGTT were significantly(p<0. 05) decreased in the liver, but were not changed significantly in soleus. Glycogen synthase activity of soleus and liver was not differ significantly in the both groups. Insulin binding at varying concentrations of insulin to crude membrane of pregnant liver was not significantly different from control. In conclusions, although these pregnant rats were normal glucose tolerance due to increased secretory response of insulin, that was correlated with progesterone concentration, pregnant rat had insulin resistance. The mechanisms of insulin resistance were not related to defect of insulin binding phase and glycogen synthase, but suggest pre-receptor and/or postreceptor phase.

The effect of regular physical exercise on glucose uptake in soleus and intravenous glucose tolerance in streptozotocin diabetic rats / 영남의대학술지

The effect of exercise on plasma insulin, free fatty acid, and glucose uptake and glycogen concentration in soleus, and intravenous glucose tolerance of streptozotocin treated, diabetic Sprague-Dawley rats were studied. Diabetic-trained animals were subjected to a regular program of treadmill running for 4 weeks. Seventy-two hours after the last training session, basal and insulin-stimulated glucose uptake was studied in incubated strips (about 20 mg) of soleus muscle in vitro. Glucose tolerance was measured with intravenous infusion of 0.5 g glucose/kg body weight. In diabetic rats, training was associated with increase glucose uptake in basal and maximal insulin concentrations, decreased fasting glucose concentrations, and increased muscle glycogen levels, but there were no changes in glucose tolerance curve and plasma insulin concentrations. These results suggest that regular running program for 4 weeks improve responsiveness of insulin on soleus muscle, but fails to cause improvement of impaired intravenous glucose tolerance in mild degree streptozotocin induced diabetic rats.