Effect of tryptophan, 5-hydroxytryptophan, serotonin, histidine, and histamine on peroxidation of lipids in liver mitochondrial membranes

Abstract

The effect of tryptophan, 5-hydroxytryptophan, serotonin, histidine, and histamine on peroxidation of lipids in rat liver mitochondrial membranes in the presence of Fe++ ions which induce this process was studied by recording very weak chemiluminescence. 5-Hydroxytryptophan and serotonin in concentrations of 10−5–10−4 M (protein concentration 1.8 mg/ml mitochondrial suspension) inhibit this process. By studying the kinetics of the initial part of the ascending branch of the “slow” burst constants of antioxidative activity were calculated: For 5-hydroxytryptophan and serotonin these were 2.2·103 and 9.8·103M−1 respectively. The antioxidant action is linked with the presence of a phenol group in the molecule of the compound tested. It is postulated that the action of 5-hydroxytryptophan and serotonin on peroxidation of lipids in membranes, besides their effect on other membrane processes, is also an important factor in the regulation of permeability of biological membranes.