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

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.Department of Molecular Pharmacology and Radiobiology, Medicobiological Faculty, N. I. Pirogov Second Moscow Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR S. S. Debov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 2, pp. 169–171, February, 1976.