Test of Insulin Secretion Capacity

Mice are surgically implanted with dual carotid and jugular catheters 5-7 days before the clamp and subjected to the clamp procedures under conscious and unrestrained conditions after fasted for 5-6 hours (15 hours for rats).

The clamp starts at t = 0 with a prime-continuous infusion of 50% glucose. Hyperglycemia (280~300 mg/dL or double the baseline glucose levels) is achieved and maintained by measuring blood glucose at t = -10, 0, 2, 5, 10, 15, 20 min and then every 20 min until 120 min and infusing 50% glucose at variable rates accordingly. Blood samples are collected at t = -10, 2, 5, 10, 15, 20, 40, 60, 90, and 120 min for determination of plasma levels of insulin (and C-peptide).

A continuous infusion of erythrocytes obtained from donor mice via cardiac puncture is given at 5 μl/min throughout the experiment period to prevent anemia from the repeated blood sampling.