GABA metabolism and cerebral protein synthesis

Quantitative evaluation of functional capacity during isoniazid therapy in Huntington's disease

Eleven patients with Huntington's disease were treated with high doses of isoniazid. In addition to clinical assessment, the functional capacity was evaluated quantitatively. The symptoms of four of the patients showed a marked improvement and their functional capacity increased. The condition of one patient with the rigid form (Westphal's variant) deteriorated, and the remaining six patients showed no change. Patients with prominent mental disturbances appeared to respond best to isoniazid therapy.

Diamine oxidase in the hen

In adult hens diamine oxidase (histaminase) activity was found in gastrointestinal tract (with the highest value in ileum), liver and spleen. Intestinal diamine oxidase is predominantly a particle-bound enzyme. In the intestine oxidation of putrescine leads to delta 1-pyrroline formation, in liver both delta 1-pyrroline and gamma-aminobutyric acid are formed. The inhibitor properties of hen intestinal and rat intestinal diamine oxidases are very similar and differ from pea seedling diamine oxidase. The natural dipeptides carnosine and anserine are relatively potent inhibitors of hen intestinal diamine oxidase.

Gamma-aminobutyric acid (GABA) formation from putrescine in guinea-pig liver during ontogenesis

1. The changes in hepatic diamine oxidase (DAO) activity of the foetal and maternal origin and their relations to GABA formation during pregnancy in guinea-pigs are described. 2. Foetal DAO activity continuously increased while the maternal enzyme from the 45th day of gestation onwards decreased. 3. Conversion of putrescine to GABA via oxidative deamination has been detected in the earliest studied day i.e. the 34th.

Metabolism of putrescine in the pregnant rat

The in vivo metabolism of 14C-putrescine injected to rats before, during and after pregnancy was studied. Within 30 min of the administration of the isotope 9-12% of the injected radioactivity was recorded as 14CO2 in the expired air and after 5 h 60% was expired. The radioactivity excreted in the urine during the first day following the 14C-putrescine administration consisted of unmetabolized putrescine, gamma-aminobutyric acid (GABA) and some unidentified compound(s). No radioactive polyamines were detected in the urine. After treatment of pregnant rats with the diamine oxidase inhibitor aminoguanidine the expiration of 14CO2 was almost completely inhibited. In the urine increased amounts of unmetabolized putrescine were excreted while the excretion of GABA and the unidentified compound(s) were decreased. In addition 14C-spermidine appeared in the urine. The in vitro metabolism of putrescine was determined by the incubation of different tissues of pregnant and non-pregnant rats with 14C-putrescine. The 14C-metabolites derived via the diamine oxidase pathway (delta 1-pyrroline, GABA, some unidentified compound(s) and carbon dioxide) varied in magnitude with the tissue investigated. GABA was found to be a main metabolite of putrescine in several tissues of the pregnant rat. The content of putrescine and spermidine was elevated in several tissues as well as the blood on the 19th day of pregnancy in rats treated with aminoguanidine, while the content of spermine was unchanged.

[Effects of 3-methylcholanthrene and 3-methylcholanthrene plus piracetam on the gamma-amino-butyric acid (GABA) content of several cerebral regions (author's transl)]

Chronic application of Piracetam decreases 3-methylcholanthrene-induced increased GABA content in the brains of rats and delays tumor appearance. The most active inhibitor of GABA-transaminase, amino oxyacetic acid (AOAA), increases the GABA content in the brain and appears to increase the tumor rate in 3-MC rats. Despite some reservations in view of results derived from investigations of only two compounds (3-MC and Piracetam) we suppose that a relation exists between effects on central nervous system and peripheral carcinogenesis. We will try to support our hypothesis further by using other compounds influencing the GABA-content of the brain.