Increase in Skeletal Muscle Blood Flow but Not in Renal Blood Flow During Euglycemic Hyperinsulinemia in Man

In order to investigate the effect of euglycemic hyperinsulinemia on skeletal muscle blood flow and renal blood flow, catheters were inserted into both femoral arteries, one femoral vein and one renal vein of 7 healthy men. Constant infusions of indocyanine-green dye (intraarterial) and of p-aminohippuric acid (intra-venous) were used to estimate leg plasma flow (ELPF) and renal blood flow (ERPF), respectively, prior to and during a euglycemic, hyperinsulinemic clamp (1.0 mU/kg.min of human insulin, serum concentrations of insulin before and during the clamp: 4.6 +/- 0.9 microU/ml and 65.5 +/- 20.6 microU/ml, respectively, t = 120 min). ERPF (basal: 1220 +/- 320 ml/min) remained unchanged throughout the period of induced hyperinsulinemia in each volunteer (mean: 1135 +/- 490 ml/min), whereas mean leg plasma flow (ELPF) rose from basal 206 +/- 99 ml/min up to 275 ml/min 90 minutes after the beginning of the euglycemic clamp study (p < 0.01). This was due to the marked rise in ELPF from 149 +/- 24 ml/min up to 243 +/- 25 ml/min (p < 0.01) seen in 5 subjects. In two men, who presented a markedly higher basal ELPF (332 and 365 ml/min, respectively), no further rise in ELPF was seen during induced hyperinsulinemia. Fractional renal extraction of insulin was unchanged during induced hyperinsulinemia (28 +/- 5%; basal: 22 +/- 18%), as was fractional extraction of insulin by the leg (10 +/- 5%; basal: 13 +/- 11%). The observed dissociation of ERPF and ELPF suggests a differential response to insulin in renal vs. leg vasculature which possibly is due to increased peripheral glucose metabolism.