Kinetics of glucose delivery to subcutaneous tissue in rats measured with 0.3-mm amperometric microsensors

The time between intravenous injection of a glucose bolus and the time the glucose concentration peaked in the subcutaneous tissue was measured in pentobarbital-anesthetized rats with implanted 290-μm-diameter amperometric sensors. Boluses of 100, 200, and 400 mg/kg body wt were injected. The glucose concentration in the jugular vein was monitored by frequent withdrawal and analysis of samples. The glucose concentration in the subcutaneous tissue was continuously monitored with the sensors. The times required for the subcutaneously implanted sensor to reach its maximum current, corrected for sensor response times, were 7.5 ± 3.9, 9.8 ± 5.5, and 10.0 ± 4.4 min for the smallest to the largest dose, respectively. The shorter delay in response to the smallest dose was statistically significant (P < 0.03). The results were consistent with dilution of the bolus in the cardiovascular system and transport of glucose by both diffusion and facilitated transport via a saturable mediator. An understanding of the differences in the dynamics of venous vs. subcutaneous response to a glucose dose is important in developing algorithms for the control of blood glucose based on a subcutaneous measurement.