Cerebral lipid metabolism in experimental hyperphenylalaninaemia: incorporation of 14C-labelled glucose into total lipids.

Abstract

Abstract—1. Effects of the administration of phenylalanine to rats on incorporation in vivo or in vitro of [U‐14C]glucose into cerebral lipids were studied during the first 5–10 days of postnatal development. In addition, the effects of added phenylalanine and its deaminated metabolites on incorporation of [U‐14C]glucose by homogenates into lipids of developing rat brain were investigated. Hyperphenylalaninaemia reduced incorporation both in vivo and in vitro of [U‐14C]glucose into cerebral lipids.2. Phenylalanine or tyrosine added in vitro at concentrations equivalent to those in the brain of the hyperphenylalaninaemic rat (0‐1 μmole/ml incubation medium) did not inhibit incorporation of [U‐14C)glucose into lipids, although at much higher concentrations of phenylalanine (36 μumoles/ml incubation medium) slight inhibition (10 per cent) of incorporation of [U‐14C]glucose into lipids was observed.3. In contrast, the deaminated metabolites in general exerted greater inhibitory effects at lower concentrations. Phenyllactic acid, in comparison to phenylpyruvic and phenyl‐acetic acid, was the most potent inhibitor of the incorporation in vitro of [U‐14C]glucose into cerebral lipids. These results indicated that these metabolites of phenylalanine were the more potent inhibitors of cerebral lipid metabolism in immature animals.