Anaphylaxis in chopped guinea pig lung. II. Enhancement of the anaphylactic release of histamine and slow reacting substance by certain dibasic aliphatic acids and inhibition by monobasic fatty acids.

The quantitative release of histamine and slow reacting substance by specific antigen from perfused, chopped, sensitized guinea pig lung has been used to study the opposing effects of monobasic and certain dibasic fatty acids on the anaphylactic reaction. The anaphylactic release of histamine and slow reacting substance is doubled by the addition of 0.5 mM of succinic or maleic acid to the reaction mixture, and enhancement is definite with as little as 0.05 mM of succinic acid. Prolonged preincubation of the tissue with the dibasic acids is not required, for 60 to 90 per cent of maximal enhancement is apparent when the antigen is added to the tissue only 10 seconds after succinic or maleic acid. The increased histamine release is not due to a qualitative change in the time course of histamine release, is not the result of increased histamine formation, and cannot be attributed to an effect on the tricarboxylic acid cycle. The enhancement seems to be due to potentiation of some step activated by the antigen-antibody interaction and common to both the release of histamine and slow reacting substance. The structural configuration required for a dibasic acid to enhance the anaphylactic reaction in guinea pig lung is quite specific; the carboxyl groups should be separated by a two carbon chain, and must be free or fixed in the cis position. The monobasic fatty acids from valeric to dodecanoic inhibit the anaphylactic release of histamine, and the concentration needed to produce 50 per cent inhibition decreases with increasing chain length. The introduction of a polar group, amino or carboxyl, into the hydrocarbon residue diminishes or abolishes inhibitory capacity. The inhibition produced by the fatty acids is neither due to calcium binding nor due to prevention of effective antigen-antibody interaction; the fatty acids probably inhibit by acting on an antigen-antibody-activated step. The inhibition of the anaphylactic release of histamine and slow reacting substance produced by caproic or decanoic acid can be reversed by the enhancing effect of succinic acid, and vice versa. Thus, compounds normally present in mammalian tissue can greatly influence the intensity of the in vitro anaphylactic reaction in the guinea pig.