EFFECT OF HYDATID FLUID ON HISTAMINE CONTENT OF RABBIT BLOOD

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Abstract
Hydatid fluid contains histamine in both free and bound conditions. The conclusion is drawn that histamine is bound, forming a low molecular complex that is fairly soluble in alc. but insoluble in ether, acetone, or chloroform. This inactive histamine "precursor" yields free active histamine after prolonged boiling in the presence of concentrated HC1. When injected intraven., hydatid fluid produces a drop of the blood histamine and very mild symptoms in the rabbit. This ability of hydatid fluid to produce a reduction of the total blood histamine is not impaired by dialysis against distilled water, nor by depro-teinization by trichloroacetic acid. From pooled samples of hydatid fluid a purified material was prepared, which has the same capacity of reducing the total blood histamine when injected intravenously into rabbits. In vitro expts. showed that hydatid fluid and the purified material derived from it were not able to liberate histamine from cells to plasma in samples of rabbit blood. In nonanesthetized rabbits, the intravenous injn. of hydatid fluid resulted in leukopenia and thrornbocytopenia, while in rabbits anesthetized with urethane leukocytosis occurred accompanied by a drop in the platelet count. In all cases, however, there was a sharp reduction of the histamine content of the blood. From these expts., the conclusion is drawn that histamine is more likely to be carried by platelets than by leukocytes, in the circulating blood of the rabbit. Hydatid fluid, or products derived from it, do not produce a fall of carotid blood pressure in the rabbit under dial or urethane anesthesia, even when a sharp reduction of the blood histamine is observed. From this fact the conclusion was drawn that there is independence between a decrease in blood histamine and the occurrence of shock.

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