The effect of ascorbic acid on malonaldehyde formation, K+, Na+ and water content of brain slices.

The ascorbate status of cortical brain slice preparation was correlated with malonaldehyde levels during the first hour of incubation in normal Krebs-Ringer phosphate medium. The ascorbate content of fresh cortical slice was 3.33 +/- 0.34 mumol/g. A portion of ascorbate was released from the tissue during incubation. The release of ascorbate was less extensive when 1 mM ascorbate was added to the medium, and in the presence of 3 mM ascorbate the initial tissue level of ascorbate was maintained during the experiment. Addition of ascorbate to the medium produced a biphasic effect on malonaldehyde formation: 1 mM ascorbate doubled, 3 mM ascorbate inhibited malonaldehyde production, as compared to control values. When in vivo cortical ascorbate level was increased by 25% through an intraperitoneal injection of 2 g/kg Na ascorbate, the relationship between tissue and medium ascorbate during incubation was unaltered, but malonaldehyde formation was delayed by approximately 30 min and the stimulatory effect of low concentration of ascorbate was not seen. During the lag period there was evidence of an ion and water pumping mechanism opposing the accumulation of water and the movement of K+ and Na+ along their concentration gradients.