Driedzic, W.R.; Clow, K.A.; Short, C.E. (2013). Glucose uptake and metabolism by RBCs fromfish with different extracellular glucose levels. Journal of Experimental Biology. 216 (3) 437-446.
The aim of the present study was to assess whether mechanisms of glucose trafficking by red blood cells (RBCs) relate to species-specific extracellular glucose levels. Atlantic cod (Gadus morhua), Atlantic salmon (Salmo salar), cunner (Tautogolabrus adspersus) and short-horned sculpin (Myoxocephalus scorpius) had plasma glucose levels of 4, 4.1, 1.95 and 0.73. mmoll(-1), respectively. Glucose uptake by isolated RBCs was measured by the initial incorporation of [6-C-14]-glucose and steady-state glucose metabolism was determined by the production of (H2O)-H-3 from [2-H-3]-glucose. Saturation kinetics of glucose uptake and inhibition of both glucose uptake and metabolism by cytochalasin B and phloretin revealed that Atlantic cod, cunner and sculpin RBCs all had a facilitated transport component to glucose trafficking. RBCs from Atlantic salmon showed a linear relationship between glucose uptake and extracellular glucose level, but exhibited clear inhibition of glucose metabolism by cytochalasin B and phloretin, suggesting a component of facilitated glucose transport that is more elusive to detect. The production of 3H2O was linear for at least 6. h and as such presents a rigorous approach to measuring glycolytic rate. Steady-state rates of glucose metabolism were achieved at extracellular levels of approximately 1. mmoll(-1) glucose for RBCs from all species, showing that within-species normal extracellular glucose level is not a primary determinant of the basal level of glycolysis. At physiological levels of extracellular glucose, the ratio of initial glucose uptake to glucose metabolism was 1.5 to 4 for all RBCs, suggesting that there is scope to increase metabolic rate without alteration of the basal glucose uptake capacity.