Increased autophosphorylation of insulin-like growth factor-I and insulin receptors in placentas of diabetic women.

Autophosphorylation of insulin and insulin-like growth factor (IGF)-I receptors were measured in lectin purified receptor preparations from placentas of normal and diabetic patients. The basal and insulin or IGF-I stimulated phosphorylation of the approximately 94 kD protein, corresponding to beta-subunit of the insulin and IGF-I receptors, were approximately 2 times greater (p less than 0.05) in placentas from diabetic patients with poor glycemic control (as judged by their serum HbA1c level) compared to the normals. The magnitude of IGF-I or insulin stimulation of the phosphorylation of the 94 kD protein was comparable in placentas from both diabetic and normal patients. Immunoprecipitation and immunodepletion of IGF-I receptor by alpha-IR3, a monoclonal antibody to IGF-I receptor, revealed the increased basal phosphorylation of the approximately 94 kD protein in placentas of diabetic patients to be associated with IGF-I and insulin receptors. The magnitude of IGF-I and insulin stimulated phosphorylation of the immunoprecipitated and immunodepleted IGF-I receptor, respectively, was the same in both normal and diabetic patients. These results suggested that the increased basal phosphorylation of the 94 kD protein in placentas from diabetic patients may be intrinsic to IGF-I and insulin receptor, however, the regulatory mechanisms effecting the increase may not be dependent on IGF-I or insulin.