Plasma histamine and coagulation time of the blood in dogs after administration of different histamine releasers

Compound 48/80, sinomenine, tween 20 and polyvinylpyrrolidone (PVP) were injected intravenously to dogs, in doses producing similar degree of profound hypotension, and changes in the plasma histamine content and coagulation time were followed on the blood from the femoral artery. After the injection of 48/80 or sinomenine plasma histamine rose rapidly and markedly, attaining its maximum within 2 minutes, but the increase was rather of a short duration. In contrast, after the injection of tween 20 or PVP a less marked increase in plasma histamine developed more slowly, but lasted longer. The blood coagulation time was prolonged in all the cases injected with 48/80, and occasionally with sinomenine. Both beginning and recovery of the prolongation of blood coagulation time were sluggish as compared with the changes of plasma histamine. Tween 20 and PVP did not induce any detectable change of the blood coagulation time. These data were discussed with reference to the sites of action of different histamine releasers.