Pharmacological significance of biogenic amines in the lungs: 5-hydroxytryptamine.

1. A technique for the spectrofluorometric analysis of 5-hydroxytryptamine, histamine, noradrenaline and dopamine in a single lung sample has been developed. The method is a combination of the extraction procedure of Shore & Olin (1958), plus the modification introduced by Hogans (1967) for the analysis of three of the four amines. The fourth amine, histamine, was analysed by the method of Shore, Burkhalter & Cohn (1959), which was combined with the analysis of the other three amines. The combined procedure consisted principally of disintegrating the lung tissue in butanol and subsequent separation of amines for measurement of fluorescence, either directly, as for 5-hydroxytryptamine, or after formation of fluorophores, as for histamine, noradrenaline and dopamine. It has been possible to analyse all four amines from a sample of the lung in which the bronchopulmonary responses have been investigated.2. The concentration of 5-hydroxytryptamine in the lung of seven species ranges from about 0.5 mug/g in the guinea-pig, dog and man to about 7 mug/g in the rabbit. The pulmonary resistance is increased after an injection of 5-hydroxytryptamine in the rat and guinea-pig.3. The guinea-pig is more sensitive to 5-hydroxytryptamine than the rat. In both animal species, the content of 5-hydroxytryptamine in the lung is elevated by administration of either 5-hydroxytryptamine or 5-hydroxytryptophan. In the rat, the administration of p-chlorophenylalanine reduces the content of 5-hydroxytryptamine in the brain but not in the lung.4. It is suggested that the 5-hydroxytryptamine contained in the lung tissue is stored mainly in the platelets and in the mast cells.