The composition of isolated cerebral tissues: ascorbic acid and cozymase

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Abstract
The total ascorbic acid of slices of rat cerebral cortex, initially 2.3 [mu]moles/g, fell by 4/5 on aerobic incubation in glucose saline for an hour. Most of the ascorbate lost to the tissue was found in the saline. Addition of ascorbate to the saline increased the ascorbate content of the tissue, which could by this means be raised above its initial level. With external ascorbate of 30-100 [mu][image], tissue ascorbate reached after 30-60 minute levels 8-10 times those of the fluid. The uptake of ascorbate by the tissue was greatly decreased when glucose and O2 were absent. Cozymase of guinea-pig cerebral cortex fell only about 15% during in vitro respiration in glucose salines, even though no cozymase or potential precursors were added; inclusion of nicotinamide did not increase tissue cozymase. The cozymase level decreased anaerobically and was not increased again by various additions. It underwent little or no further change when anaerobic glycolysis was greatly decreased by electrical pulses or by K salts.