Effects of standard anticoagulants and storage procedures on plasma glucose values in seals

Standard methods for the preservation of vertebrate blood samples for glucose analysis include collecting and storing the blood in evacuated tubes containing sodium fluoride (glycolytic inhibitor) and potassium oxalate (anticoagulant). We found that blood collected from 5 seals by venipuncture and transferred into these tubes had a significantly (P less than 0.05) lower plasma glucose value than blood transferred into tubes containing heparin. In species in which RBC glucose concentration is significantly less than that in the plasma, fluoride and oxalate-induced hemolysis dilutes the plasma with cytoplasm and lowers the measured concentration of glucose in plasma. Therefore, although plasma glucose is used extensively in experimental and clinical analyses, standard techniques for handling the blood may create errors that could confuse comparisons between individuals or species.