Summary.Our previous work has suggested the presence of an insulin resistance in the adult offspring of streptozotocindiabetic pregnant rats. In this study we used the euglycaemic hyperinsulinaemic clamp technique with an isotope-dilution method to define and quantify this postulated insulin resistance in adult offspring of streptozotocin-diabetic rats. Under basal conditions, these rats had a lower body weight than control rats, but their glucose and insulin concentrations were normal. During the hyperinsulinaemic clamp, the steady-state glucose infusion rate was significantly lower in the offspring of streptozotocin-diabetic rats than in both ageand weight-matched controls, indicating insulin resistance. Basal peripheral tissue glucose utilization was normal in the offspring of streptozotocin-diabetic rats, but the dose-response curve was shifted to the right: insulin concentrations causing half-maximal stimulation of glucose utilization were increased by about 60% in the offspring of diabetic rats; the maximal stimulation of glucose utilization, however, was unaltered. Basal hepatic glucose production was normal, but again, half-maximal suppression of glucose production occurred at insulin concentrations 50% higher than in controt rats; in addition, the maximal suppression of glucose production was significantly decreased, even at insulin concentrations of 5700 btU/ml. These data are evidence for an insulin resistance in the adult offspring of streptozotocin-diabetic rats, characterized by: (1) a decreased insulin sensitivity by peripheral glucose-utilizing tissues, and, (2) a decreased sensitivity and responsiveness of the liver.
Key words:Insulin resistance, euglycaemic hyperinsulinaemic clamp, offspring of streptozotocin-diabetic rats.Metabolic changes in the pregnant streptozotocindiabetic rat have been shown to affect fetal development and fetal glucose homeostasis [1, 21. A severe hyperglycaemia ( > 20 mmol/1) in the maternal rat results in hyperglycaemia and hypoinsulinaemia of their fetuses. On histology and electronmicroscopy, we found evidence of islet hypertrophy, Beta-cell hyperplasia and Beta-cell degranulation in these fetuses: a 'Beta-cell exhaustion phenomenon' is probably the cause of decreased insulin levels in fetal serum [1,2]. Malnutrition of the newborn rats by their mothers, causes frequent postnatal death and subnormal glucose and insulin levels in the survivors until weaning [1,3]. Body weight in the offspring of severely hyperglycaemic rats is significantly lower than normal from day 20 of gestation and it remains significantly lower during postnatal life: during the lactation period and after weaning [1][2][3]. The adult offspring of severely hyperglycaemic pregnant rats (SDF-rats) have a normal pancreas on histology and normal serum glucose and insulin concentrations in basal conditions, but their glucose tolerance is clearly impaired [3,4]. Data from an in vivo 123I-insulin captation study would suggest an insulin resistance in SDF-rats [5]. In this study, we used the euglycaemic ...