Insulin Absorption and Subcutaneous Blood Flow in Normal Subjects During Insulin-Induced Hypoglycemia*

We studied the effects of insulin-induced hypoglycemia on the absorption of 10 U 125I-labeled soluble human insulin injected sc in the thigh in 10 normal subjects. The disappearance of 125I from the injection site was followed by external gamma-counting. Subcutaneous blood flow (ATBF) was measured concomitantly with the 133Xe washout technique. The plasma glucose nadir [mean, 2.0 +/- 0.1 (+/- SE) mmol/L] occurred at 33 +/- 3 min and resulted in maximal arterial plasma epinephrine concentrations of approximately 6 nmol/L. From 30 min before to 60 min after the glucose nadir the [125I]insulin absorption rate was depressed compared to that during normoglycemia. The first order disappearance rate constants were reduced by approximately 50% (P less than 0.01) during the first 30-min interval after the glucose nadir. During the same period ATBF increased by 100% (P less than 0.05). The results suggest that in normal subjects the absorption of soluble insulin from a sc depot is depressed in connection with hypoglycemia, despite considerably elevated ATBF.