Figure 1: Study design and clamp protocols. Blood samples (~50 µl each) were withdrawn from the carotid at 10-min intervals to determine plasma glucose, insulin, hepatic glucose production and glucose disposal rates. Plasma [3-3H] glucose radioactivity was measured from the supernatants of barium hydroxide-zinc sulfate precipitates of plasma samples after drying [17]. The rates of total body glucose uptake and hepatic glucose production were calculated using Steele’s equations from plasma samples during the last 20 minutes of each clamp period [17].