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Concentrations of insulin, proinsulin, and C-peptide were measured in portal and peripheral venous blood in six nondiabetic, nonobese subjects. Portal vein samples were obtained by umbilical vein catheterization. Three subjects were studied with intravenous infusion of 25 g glucose, and three with 30 g arginine. Insulin and proinsulin were determined in the(More)
In seven patients with factitious hypoglycemia due to the surreptitious injection of insulin, we made the diagnosis by measurements of plasma insulin and C-peptide immunoreactivity (in seven patients), facilitated by the finding of circulating insulin-binding antibodies (in two patients). The simultaneous demonstration of low plasma glucose, high(More)
A 51-year-old, nonobese man with diabetes mellitus had marked hyperinsulinemia (70 to 120 muU per milliliter; 502 to 860 pmol per liter) and fasting hyperglycemia (140 to 170 mg per 100 ml; 7.8 to 9.4 mmol per liter). Plasma proinsulin, glucagon, growth hormone, and cortisol levels were normal; insulin antibodies and insulin-receptor antibodies were not(More)
Hypoglycemia coexisting with very low plasma immunoreactive insulin concentrations was found in a 78-year-old woman with an insulinoma. However, the absolute proinsulin levels during hypoglycemia were elevated (0.9 to 1.4 ng/ml), accounting for 66.5% of the total circulating immunoreactive insulinlike material. The raised serum proinsulin concentrations(More)
Insulin isolated from the pancreas of a diabetic patient with fasting hyperinsulinaemia showed decreased activity in binding to cell membrane insulin receptors and in stimulating cellular 2-deoxyglucose transport and glucose oxidation. Chemical studies suggest that the isolated hormone is a mixture of normal insulin and an abnormal variant which contains a(More)
Peripheral serum insulin and C-peptide concentrations during oral glucose tolerance tests were measured in 10 nondiabetic Pima Indians and 10 nondiabetic Caucasians with varying degrees of obesity. Although both insulin and C-peptide levels were elevated in the Indians compared to the Caucasians (p less than 0.05), hepatic insulin extraction, measured by(More)
The removal of bovine proinsulin by the isolated perfused rat liver has been studied and the results compared with the removal of insulin. At high concentrations of insulin (> 180 ng/ml) the removal process was saturated and the t(1/2) varied between 35 and 56 min. With low initial insulin levels the disappearance followed first-order kinetics, the mean(More)
The variation in cross-reactivity of human and porcine insulins and proinsulins was determined with a number of insulin antisera. The relative immunoreactivity of insulin and proinsulin with these antisera ranged from a ratio of 1.08 to 5.7 on a molar basis. The displacement curves of human insulin and proinsulin were not parallel, and the relationship of(More)