Long-term portocaval shunt and changes in rat brain amine systems

Brain amine system parameters were investigated in Wistar rats sacrificed 7 months following portocaval shunt or sham operation. After removal of the cerebellum and pons, the hypothalamus and remaining parts of the brain were examined. Histamine was assayed radioenzymatically; indoles and catechols by HPLC with electrochemical detection; spermidine and spermine by HPLC with fluorometry. MAO-A and MAO-B activities were estimated with radioassays employing serotonin and beta-phenylethylamine, respectively and specific inhibitors, clorgyline and deprenyl. Long-term portocaval shunt did not significantly alter cerebral catecholamines, serotonin, spermidine or spermine concentrations. However, brain histamine and 5-hydroxyindoleactic acid were significantly raised. Of the MAO enzymes only MAO-B activity was elevated (ca. 25%, p < 0.05) in the hypothalamus but not in the rest of the brain. The kinetic measurements suggest an adaptive change in MAO-B protein synthesis. The data suggest changes evoked by portocaval shunt in brain amine systems are permanent and there are species differences in MAO enzymes' response to higher substrate supply.