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Biochemical and developmental features of experimental phenylketonuria induced by L-ethionine in suckling rats
J Gehrmann1, K Schott, V Neuhoff
1Max-Planck Institut für Experimentelle Medizin, Forschungsstelle Neurochemie, Göttingen, Federal Republic of Germany.
Insights
L-ethionine administration in suckling rats induced hyperphenylalaninemia and phenylketonuria, impairing brain development. However, severe side effects limit its use as a phenylketonuria model.
Area of Science:
- Biochemistry
- Neuroscience
- Toxicology
Background:
- Phenylketonuria (PKU) is a genetic disorder characterized by impaired phenylalanine metabolism.
- Animal models are crucial for understanding PKU pathogenesis and testing interventions.
- L-ethionine is an amino acid analog that can induce metabolic disturbances.
Purpose of the Study:
- To investigate the effects of L-ethionine administration on amino acid metabolism and brain development in suckling rats.
- To evaluate L-ethionine as a potential animal model for phenylketonuria.
Main Methods:
- Suckling rats were subcutaneously injected with L-ethionine.
- Phenylalanine hydroxylase activity, amino acid concentrations, ATP content, and cathepsin D activity were measured.
- Body weight and mortality were monitored.
Main Results:
- L-ethionine induced hyperphenylalaninemia and phenylketonuria by inhibiting phenylalanine hydroxylase.
- Female rats showed greater sensitivity to L-ethionine.
- Significant alterations in serum and brain amino acid profiles, decreased ATP, and increased cathepsin D activity were observed.
- Hyperphenylalaninemia and amino acid imbalances impaired brain development.
- Side effects included high mortality, weight loss, and delayed development.
Conclusions:
- L-ethionine effectively models hyperphenylalaninemia and phenylketonuria in suckling rats.
- The observed side effects, including developmental delays and mortality, restrict its utility as a precise model for classic phenylketonuria.
- Further research is needed to refine ethionine-induced models or explore alternative approaches for PKU research.
Abstract:
Suckling rats were injected subcutaneously with doses of L-ethionine (0.1 mumole/g body wt) at intervals of 12 hr. In the latter group, phenylalanine hydroxylase was effectively inhibited in vivo resulting in hyperphenylalaninemia and phenylketonuria. Due to the well-known sex-specific differences in L-ethionine metabolism female rats were much more affected by chronic administration of L-ethionine. The underlying mechanism of enzyme inhibition by ethionine could be disturbed protein synthesis and impaired protein phosphorylation, which was suggested by pronounced decreases in ATP content in liver. In the high dosage group depletions mainly of the branched-chain amino acids and lysine occurred in serum and brain, whereas the concentrations of methionine and tryptophan were increased. Tyrosine tended to be decreased in the course of hyperphenylalaninemia. Hyperphenylalaninemia and other resulting amino acid imbalances obviously impaired brain development during the early postnatal period. Concomitantly with reductions in protein concentrations, the activity of cathepsin D, a major intralysosomal acid proteinase, was increased in brain, suggesting also higher protein catabolism in brain. Side effects of this treatment, however, were higher mortality, loss of body weight, and a general impression of delayed development, resembling a state of undernutrition to some extent. These obvious side effects of ethionine limit the usefulness of ethionine as a suitable model for classic phenylketonuria in suckling rats.