INSULIN INCREASES BLOOD-VOLUME IN HUMAN SKELETAL-MUSCLE - STUDIES USING [O-15]CO AND POSITRON EMISSION TOMOGRAPHY

High insulin concentrations increase blood flow in the leg, but it is unknown whether this effect is associated with a change in muscle bloo d volume. In the present study, we used positron emission tomography c ombined with inhalation of [O-15]carbon monoxide to quantitate the eff ect of insulin on skeletal muscle blood volume in humans. The reproduc ibility of the method was determined from two consecutive measurements performed in the basal state in five normal subjects. The coefficient of variation of the repeated measurements was 3.0 +/- 1.8%. In 14 nor mal subjects [age 35 +/- 3 yr, body mass index 24.9 +/- 1.3 (SE) kg/m( 2)], skeletal muscle blood volume was determined in the femoral region in the basal state and during euglycemic hyperinsulinemia (serum insu lin 3,200 +/- 190 pmol/l). The mean muscle blood volume was 3.3 +/- 0. 1 ml/0.1 kg muscle in the basal state. Insulin increased muscle blood volume by 9 +/- 2% to 3.6 +/- 0.2 ml/0.1 kg muscle (P < 0.01). The rat e of whole body glucose uptake was 53 +/- 6 mu mol . kg(-1). min(-1) a nd correlated with muscle blood volume during insulin stimulation (r = 0.65, P < 0.02). We conclude that high insulin concentrations exert a true vasodilatory effect in human skeletal muscle.