Glycometabolic status in +/b and b/b rats. Glucose tolerance test (GTT) (A) and insulin tolerance test (ITT) (B) were carried out after 6 h fasting. Twelve-week-old male b/b rats and age-matched +/b rats (n = 6 each group) were injected with d-glucose (1.5 g/kg body wt) or insulin (1 IU/kg body wt), and blood glucose was measured at 10, 20, 30, 45, 60, and 90 min after ip injection.