Effect of phospholipase and trypsin on histidine uptake by mouse brain slices

Abstract

1. 1. Mouse brain slices accumulated histidine from a wide range of external histidine concentrations. On 60 min incubation in oxygenated Krebs-Ringer bicarbonate medium supplemented with glucose, saturation was reached with 20 mM histidine, the uptake being 32 μmoles/g tissue. 2. 2. Phospholipases A and C inhibited histidine uptake by brain slices from varying histidine concentrations. Initial influx of histidine into brain slices pretreated with phospholipase A was inhibited to an extent that depended on enzyme concentration. 3. 3. Trypsin did not interfare with histidine uptake. Preincubation of brain slices with trypsin enhanced the inhibiting effect of phospholipase A on uptake of histidine. 4. 4. Treatment of brain slices with phospholipase A under conditions required to completely stop histidine accumulation resulted in slight hydrolysis of their phosphatidylcholine and phosphatidylethanolamine.