The rate of the root shift in eel red cells and eel haemoglobin solutions.

1. We have measured the rate of the exchange of O(2) between eel red blood cells and their suspending fluid in a modified Hartridge-Roughton continuous-flow rapid-reaction velocity apparatus using an oxygen electrode to follow the progress of the reaction.2. The half-times for the uncomplicated oxygenation and deoxygenation reactions in red cells at 24 degrees C were approximately 0.025-0.08 sec.3. The rate of the Root shift in cell suspensions varied widely, depending on the initial condition of the CO(2)-bicarbonate buffer system in the suspending fluid, with the rate of oxygenation or deoxygenation of the intracellular haemoglobin as an upper limit.(a) The most rapid Root shift was produced by a change in extracellular P(CO2) with minimal contributions from CO(2) hydration-dehydration reactions in the suspending fluid or from ion exchanges across the membrane, and had a half-time as short as 0.040 sec.(b) The slowest Root shift was produced by an increase in the extracellular lactic acid concentration in the absence of any form of CO(2) or in the presence of acetazolamide. This process is presumed limited by the rate of H(+) or OH(-) transfer across the membrane and had a half-time in excess of 10 sec.(c) The Root off-shift produced by an increase in P(CO2) plus a decrease in extracellular pH showed no significant trend as temperature was lowered from 30 degrees to 11 degrees C.(d) The Root on-shift produced by a decrease in P(CO2) and increase in extracellular pH had a half-time of 3 sec at 30 degrees C, 9 sec at 24 degrees C and 20 sec at 11 degrees C. These changes appeared limited by the uncatalysed rate of extracellular CO(2) hydration.4. Root off- and on-shifts in cell haemolysates at 24 degrees C, produced predominantly by changing pH but with unavoidable subsequent readjustments of the CO(2)-bicarbonate buffer systems, had an initial rapid phase with half-times as low as 0.01 sec. However, the curves were not monotonic, although they became so in the presence of carbonic anhydrase, indicating partial rate limitation by CO(2) reactions.