The inhibition of glucose uptake to erythrocytes: microwave dielectric response.

Dielectric spectroscopy has been used in the study and development of non-invasive glucose monitoring (NIGM) sensors, including the range of microwave frequencies. Dielectric relaxation of red blood cell (RBC) cytosolic water in the microwave frequency band has been shown to be sensitive to variations in the glucose concentration of RBC suspensions. It has been hypothesized that this sensitivity stems from the utilization of D-glucose by RBCs. To verify this proposition, RBCs were pretreated with inhibitors of D-glucose uptake (cytochalasin B and forskolin). Then their suspensions were exposed to different D-glucose concentrations as measured by microwave dielectric spectroscopy (MDS) in the 500 MHz-40 GHz frequency band. After incubation of RBCs with either inhibitor, the dielectric response of water in the cytoplasm, and specifically its relaxation time, demonstrated minimal sensitivity to the change of D-glucose concentration in the medium. This result allows us to conclude that the sensitivity of MDS to glucose uptake is associated with variations in the balance of bulk and bound RBC cytosolic water due to intracellular D-glucose metabolism, verifying the correctness of the initial hypothesis. These findings represent a further argument to establish the dielectric response of water as a marker of glucose variation in RBCs.