Glucose uptake and metabolism by red blood cells from fish with different extracellular glucose levels

• Published in: Journal of Experimental Biology
• Main Authors: Driedzic, William R., Clow, Kathy A., Short, Connie E.
• Format: Text
• Language: English
• Published: Company of Biologists 2013
• Subjects: Research Articles; atlantic cod; Atlantic salmon; Gadus morhua; Salmo salar
• Online Access: http://jeb.biologists.org/cgi/content/short/216/3/437; https://doi.org/10.1242/jeb.079178

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 mmol l−1, respectively. Glucose uptake by isolated RBCs was measured by the initial incorporation of [6-14C]-glucose and steady-state glucose metabolism was determined by the production of 3H 2 O from [2-3H]-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 3H 2 O 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 mmol l−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.