Basal Phase. D-[3,3H]glucose (3H-glucose, Amersham Pharmacia Biotech, Uppsala, Sweden) was administered as an initial 2 min priming infusion (~30 × 106 dpm/kg) followed by a constant infusion (1 × 106 dpm/min/kg). Arterial blood samples (~100 μL) were collected at 40, 60, 70, and 80 min following commencement of tracer administration directly from the carotid catheter into potassium EDTA containing tubes (Microvette CB300, Sarstedt, Nümbrecht, Germany), for determination of plasma 3H-glucose (see below) and plasma glucose levels using a YSI 2700 glucose analyzer (YSI Incorporated, Yellow Springs, OH, USA). Samples collected at 60, 70, and 80 min were used to define the basal phase plasma 3H-glucose steady state and the subsequent target blood glucose level for the clamp state.
