To study the long-term effects of exposure to maternal hyperglycemia and insulin deficiency in utero, we used the syngeneic islet transplanted streptozotocin-diabetic rat model of diabetes in pregnancy and examined insulin secretion and action in 6-month-old offspring. Female rats were rendered diabetic with streptozotocin and then transplanted with 2500, 750, or 500 islets. Control animals were also studied, and one group whose islet transplants failed remained diabetic. During pregnancy, plasma glucose levels in the diabetic rats and the groups receiving 500 and 750 islets were 24.7 +/- 1.0, 15.3 +/- 1.4, and 7.9 +/- 0.5 mmol/liter, respectively, all significantly greater than the control value (5.6 +/- 0.3 mmol/liter; P < 0.05). The plasma glucose level in the 2500 islet group was 6.2 +/- 0.2 mmol/liter, which was not significantly higher than the control value. When the offspring were studied at 6 months, there was no significant difference between groups in either glucose or insulin levels after iv glucose, although acute insulin secretion tended to be higher in the offspring of the diabetic animals. A study of insulin action with the euglycemic clamp at two insulin levels showed that insulin sensitivity was reduced in the offspring of diabetic animals vs. controls (1.97 +/- 0.24 vs. 7.58 +/- 0.95 mumol/liter x 100/kg/min.pmol/liter; P < 0.05). Insulin sensitivity was also significantly reduced in the 2500, 750, and 500 islet group offspring (4.81 +/- 0.57, 4.82 +/- 0.64, and 4.01 +/- 0.63 mumol/liter x 100/kg/min.pmol/liter; P < 0.05) compared to that in the control. There were no differences in insulin sensitivity between male and female animals. In summary, animals displaying maternal insulin deficiency have offspring who are insulin resistant without any evidence of iv glucose intolerance or diminished insulin secretion.