Measurement of Oxygen Consumption in the Rat Lens with a Flow Respirometer

¹ Department of Anatomy, The University of Michigan Medical School, Ann Arbor, Mich.

The oxygen uptakes of individual rat lenses are measured in a new recording respirometer based on the oxygen electrode. An automatically controlled double flow system permits the electrode to be calibrated in the course of a determination toithout disturbing the steady state at the lens. The rate of oxygen consumption of a lens is flow-independent above a critical volume flow rate at which the oxygen utilization is 17 to 18 per cent. That the apparatus can measure, through at least 50 per cent utilization, uptake proportional to the amount of tissue is shown on varied numbers of amphibian embryos. Rat lenses averaging 23.9 mg. fresh weight have under standard conditions (bicarbonate-buffered TC199 medium, pH 7.5, 20 per cent O₂, 37° C.) an oxygen uptake of 0.75 ± 0.08 µl O₂ per lens-hour. The rate is not changed in phosphate, Tris buffer, or by substitution of Tijrodes solution for TC199. Respiration would appear to account for less than 4 per cent of glucose utilization in vitro at this oxygen tension.