The relationship of rat lens respiration to oxygen concentration and pH.

As the oxygen content of the medium is raised, rat lens respiration increases abruptly to a plateau level at 20 to 30 per cent Ot, and then rises continually through at least 95 per cent Or. Two oxidation reactions may be involved. Oxygen uptake is unexpectedly more active in the acid range than in the alkaline, in a pattern again suggestive of two oxidative mechanisms. The possible identity of the respiratory component active in high oxygen levels and at low pH is considered. It is probably not significant under conditions obtaining in vivo. On this assumption it is estimated that respiration accounts for less than 33 per cent of the energy derived from glucose catabolism in the lens.