Histamine release from the isolated guinea-pig heart by compound 48/80.

Histamine release was observed in isolated guinea-pig heart perfused by the constant flow method, after bolus injection of 50-200 micrograms of compound 48/80. Practically all the histamine is released within the first 3 min after 48/80. This effect is inhibited by the addition of sodium cyanide (300 microM) to a glucose-free perfusion fluid and also by the removal of calcium of the medium in presence or absence of EDTA (100 microM). This dependence on metabolism and calcium is highly suggestive of a non-cytotoxic action of 48/80 on the mast cells of guinea-pig heart.