Intravenous injection of a definite amount of adrenaline caused a distinct increase in the histamine equivalent of the blood plasma and thoracic lymph, especially in the former, and a slight increase in the histaminase activities of both fluids. Intravenous injection of acetylcholine, nicotine, and atropine also tended to increase the lymph histaminase activity but no increase was observed in the histamine equivalents of the plasma and lymph. Dibenamine itself failed to effect any change in these values in the plasma and lymph, but suppressed the foregoing effects and lymphagogic action of adrenaline. Intravenous injection of the corbicula (Corbicula japonica Prime) extract did not effect increase of the histamine equivalent, either in the plasma or lymph, but markedly elevated the lymph histaminase activity, while no such increase was observed in the plasma histaminase activity. ATP exhibited a lymphagogic action but did not affect the the histaminase activities of the plasma and lymph. It may therefore be that the action of the corbicula extract on lymph histaminase cannot be due to adenine nucleotides liberation, which was suggested to occur by Takaoka (1956) in our laboratory. During serum anaphylactic shock a marked increase of histamine equivalent was observed in the plasma and lymph. In this case the increase of histaminase activity was very marked in the lymph but was slight in the plasma. These changes are almost identical with those already reported for peptone. In in vitro experiments, all the drugs tested during the present series of experiments, as well as histamine, sinomenine, and peptone failed to cause any changes in the activities of the histaminase with the concentrations even higher than expected to reach in the plasma and lymph. According to the foregoing observations, the mechanism whereby an increase occurs in
histaminase activities of the body fluids may be at least of two kinds; the one that mediated by a certain pharmacological action of histamine and the other that seen in the case of peptone, corbicula extract, and anaphylactic shock.