Insulin binding of erythrocytes in hypoinsulinemic diabetics and its relationship to metabolic states.

We studied the insulin binding of erythrocytes from 26 "well-controlled" (FBG less than 120 mg/dl), and 28 "poorly-controlled" (FBG less than 120 mg/dl) non-obese diabetic patients, and 51 age-matched normal subjects. The capacity of insulin receptors was significantly decreased in well controlled (33.7 +/- 2.2) and poorly controlled (32.4 +/- 2.3) groups compared with normal subjects (43.1 +/- 2.3 sites/cell), while fasting insulin levels of diabetics were comparable to normal subjects but their insulin response to a glucose challenge was considerably decreased. However, the "empty sites" affinity (Ke) was significantly increased in both the well controlled group (5.2 +/- 0.3) and the poorly controlled group (4.8 +/- 0.3) compared with normal subjects (4.0 +/- 0.2 X 10(8) M-1). Thus, the capacity of insulin receptors to bind erythrocytes was decreased but binding affinity was increased in hypoinsulinemic diabetics. The amount of insulin bound in well-controlled diabetics was comparable to that in control subjects at physiological insulin concentrations.