Microcalorimetric measurements of heat production in human erythrocytes. III. Influence of pH, temperature, glucose concentration, and storage conditions.

Heat production in human erythrocytes has been measured under different conditions of pH, glucose concentration, and temperature. Storage conditions have also been varied. The erythrocytes, which were from healthy subjects, were suspended either in autologous plasma or in phosphate buffer. The heat effect, P, was shown to increase linearly in the physiological pH range: 1.2% per 0.01 pH unit. Variation of the glucose concentration within a wide range, 3-32 mmol/1, did not affect the P value. The temperature coefficient for P was determined to be Q10 = 2.8 for the temperature range 32-42 degrees C. A constant energy of activation was found, 82.6 kJ/mol, for the temperature range 25-42 degrees C. When the erythrocytes were stored at 4 degrees C, P values (measured at 37 degrees C) increased initially by 6%/h. After 24 h of storage P was about 50% higher than the initial value. Determinations of glucose consumption were made in parallel with most of the calorimetric experiments.