Microcalorimetric measurements of heat production in human erythrocytes. Heat effect during methylene blue stimulation.

The metabolic activity in human erythrocytes during stimulation with 10(-4) mol/l methylene blue has been studied by a microcalorimetric method. Simultaneous measurements were performed on cells from the same preparation suspended in different media. Mean values for the ratios between heat effect values were 7.1 +/- 1.0, 7.4 +/- 0.8, and 10.2 +/- 1.7 (+/- S.D.) for cells suspended in plasma, serum, and glucose phosphate buffer, respectively. All heat effect values were corrected to pH 7.40 using the correction factor found in the present work (0.4 % per 0.01 pH unit). The present calorimetric results are in qualitative agreement with previous reports of other investigators concerning the stimulating effect of methylene blue and the influence of pH on the pentose phosphate pathway.