The Sites of Action of some Histamin-Releasing Substances in the Dog

1. The rates of histamine release from the liver, skin and muscle by four kinds of histamine-releasing substances, sinomenine, compound 48/80, tween 20 and polyvinylpyrrolidone (PVP), were compared by intravenous injection in dogs, each in a dosage to cause a fall of approximately 80 per cent in the arterial blood pressure. 2. By compound 48/80, the rates were especially marked from the liver and muscle and only slight from the skin, while those by sinomenine, tween 20 and PVP were largest from the skin, followed by those from the liver and muscle, in that order. The rate of histamine release from the skin by PVP was characteristic in that it was far larger than that by other releasers. 3. On direct application of the drug solutions to the excised tissues of the liver and skin the rates of release of histamine differed only slightly by the tissue in any of these releasers 4. Some considerations were given on the reason for the different ratios by the organ of in vivo histamine release though as yet no definite conclusion could be drawn.