Glucose Oxidation and Insulin Receptors in Isolated Adipocytes from Late Pregnant Rats

Abstract

Increased insulin resistance is one of the characteristics of metabolism during pregnancy.We studied the action of insulin on glucose oxidation and the insulin receptors using isolated adipocytes prepared from late pregnant rats in order to clarify the mechanism of the insulin resistance.The insulin action on glucose oxidation was estimated by measuring the amount of ¹⁴CO₂ converted by adipocytes from (1-¹⁴C) glucose during 60 min at 37°C. The insulin receptors were assessed by measuring the ¹²⁵I-insulin bound to the adipocytes during 60 min at 37°C or during 90 min at 24°C. The glucose oxidation was significantly decreased in the pregnant rat adipocytes with or without insulin.The amount of ¹⁴CO₂ converted from (1-¹⁴C) glucose by adipocytes from pregnant and nonpregnant rats was 2.81±0.49 and 4.62±0.54 without insulin, and 16.04±2.10 and 26.1±3.43 (n=7, mean±SEM) with 25ng/ml insulin, respectively.There was no significant difference in the ¹²⁵I-insulin binding at each insulin concentration between the pregnant and nonpregnant rats.There was also no significant difference in the degradation of ¹²⁵I-insulin during the incubation time.
These results suggest that isolated adipocytes from late pregnant rats are resistant to insulin on glucose oxidation and that this insulin resistance is due to certain changes at the postreceptor sites.