[Insulin receptors in fat tissue of human and rat during pregnancy]

Insulin receptors in fat cell membranes (10(5)g pellets) were investigated by a conventional incubation method in pregnant and nonpregnant rats or women. Insulin binding in pregnant L20 rats was 8.1 +/- 2.1% (M +/- SD) less than that in nonpregnant rats (14.5 +/- 3.5%) in peripheral adipose tissues (p less than 0.05). In the former a reciprocal rise in the serum insulin level was observed. In pregnant women, insulin binding was determined in subcutaneous fat tissues obtained at cesarean section or other laparotomy. Insulin binding was 29.3 +/- 8.9% in nonpregnant women, and it did not change in early pregnancy (34.3 +/- 6.2%, NS). However, it decreased obviously in late pregnancy (20.4 +/- 6.4%) (p less than 0.05). Scatchard analysis indicated that the decrease in insulin binding was due to the changes in the number of insulin receptors in fat cell membranes. Their Kd values were indistinguishable from each other in rats and women. In addition, insulin binding correlated significantly with Insulin Sum, Glucose Sum at 75g OGTT, TG and FFA in serum. These results suggested that insulin receptors in adipose tissues were suppressed in late pregnancy, and this might be the cause of the "insulin resistance" observed in the maternal body in late pregnancy.