Exercise-induced increase of methaemoglobin concentration and low cooperativity in haemoglobin-oxygen binding at rest...

Relations between oxygen consumption, physical effort and parameters characterizing oxygen transport by red blood cells [rbc] before and after exercise were assessed in 32 healthy persons. The oxygen affinity of haemoglobin was studied in rbc by several measurements of pO2, pCO2, pH and HbO2 in samples of heparinized venous blood equilibrated with the gas compartment containing decreasing concentrations of O2 and 5% CO2. The actual oxygen affinity significantly decreased after exercise with the values of log p50 [act] equal 1.42 +/- 0.1 at rest and 1.51 +/- 0.12 after the effort; the difference was assessed by the nonparametric test of pairs [p less than 0.05]. No effect of exercise was noted on the mean values of apparent p50, a parameter sensitive to the intraerythrocytic regulators of haemoglobin-oxygen affinity. In subjects with the highest values of efficiency of oxygen utilization [Eff], i.e. the lowest oxygen consumption during maximal effort, the values of Eff were however found to be correlated with the cooperativity in Hb-O2 binding at rest [r = 0.565] and with the exercise-induced changes in metHb concentration [r = 0.258]. The exercise-induced changes in metHb concentration correlated with the exercise-induced change in apparent p50 [r = 0.496].