Arterial concentration and forearm extraction of glucose and insulin during the early phase of a glucose infusion.

The concentrations of glucose and insulin were determined with high precision at half minute intervals in arterial and deep forearm vein blood after a bolus injection of glucose (4 g), followed by a constant i. v. infusion (200 mg/min), in four healthy subjects. The values for the deep vein were corrected for the transit time, which was determined by injection of Cardio-green. Arterial glucose peaked at the end of the bolus injection, venous glucose 1 1/2 min later. Arterial insulin reached its maximum later than glucose, after 2 1/2-4 min. The venous insulin reached its maximum later and was much lower than the arterial level, in two cases only around 50% of the arterial concentration. It is concluded that early after glucose administration there is a considerable extraction of both glucose and insulin by the forearm. Since the insulin extraction was quite variable venous insulin concentrations cannot be used for the assessment of early insulin response to glucose.