Actrapid human insulin

Hypoglycaemia was induced in the fed state by intravenous administration of a bolus dose of insulin (5.25 μg/kg in 10 mL saline, Actrapid human Insulin, Novo Nordisk). Arterial blood samples (1 mL) were taken at 5–10-min intervals for 30 min before to 60 min after insulin administration to monitor blood glucose concentrations, with larger samples (5 mL) taken immediately before and at 60 min after the insulin bolus in a subset of each treatment group to measure the plasma cortisol and ACTH concentrations.

After fasting overnight, a bolus of insulin (approximately 10–12 pmol in 1 mL saline, Actrapid human insulin, Novo Nordisk) was given intravenously via one of the venous catheters followed immediately by a continuous infusion for 2 h (48 pmol insulin/kg/min). After 15 min of insulin infusion, glucose (25% dextrose solution, Arnold, Shrewsbury, UK) was infused via the other venous catheter at a known variable rate to maintain blood glucose levels at the mean glucose concentration (±5%) measured over the 30-min basal period before insulin administration. Arterial blood samples (0.2 mL) were taken for blood glucose measurements every 5 min with larger samples (5 mL) drawn for the measurement of plasma insulin concentrations immediately before infusion and again at 90, 105 and 120 min after starting the insulin infusion once steady state had been achieved. Insulin sensitivity of glucose metabolism was measured as the steady-state rate of glucose infusion (μmol/kg/min) during the second hour of insulin infusion divided by the steady-state insulin concentration during this period (pmol/L). Insulin clearance was calculated as the rate of insulin infusion (48 pmol/kg/min) divided by the steady-state insulin concentration (pmol/L).

A total of 160 rats were randomly divided into five groups (n=32 per group). (1) Control: rats were administrated with 0.9% sterile saline solution (1.5 ml/rat), by intragastric administration 30 min before transferring into the containers of the acceleration device without rotation for 2 h. (2) Exposure: rats were administrated with 0.9% sterile saline solution (1.5 ml/rat), by intragastric administration 30 min before 2-h acceleration. (3) Exposure+Sco: rats were administrated with Scopolamine (1 mg/kg), dissolved in 0.9% sterile saline solution (1.5 ml/rat), by intragastric administration 30 min before 2-h acceleration. (4) Exposure+Ins: rats received intraperitoneal injection of insulin 30 min before 2-h acceleration (1 unit/kg, Actrapid human insulin, Novo Nordisk, Bagsvaerd, Denmark). (5) Exposure+protein combined with carbohydrate (CPL): rats were administrated with glucose (4.8 g/kg), maltose (2.4 g/kg), casein (1.8 g/kg) and leucine (0.6 g/kg), dissolved in 0.9% sterile saline solution (1.5 ml/rat), by intragastric administration 30 min before 2-h acceleration.