Nature of the Capillary Permeability Factor Present in Extracts of Normal Tissues

Abstract

Menkin has shown that inflammatory exudates of various kinds have the property of increasing capillary permeability as demonstrated by the so-called trypan blue test in rabbits. This consists in the localization and concentration of intravenously injected trypan blue at the site of an intradermal injection of the exudate or preparations thereof. He ascribes this property to a specific substance in the exudates which he terms leukotaxine, and which, presumably, is liberated into the exudate from the injured tissues. Bier and Planet, as well as Rigdon, have reported that extracts of normal tissues exhibit this capillary permeability effect. Since Rocha e Silva and Bier have shown that suitable concentrations of histamine give a positive trypan blue test, and since Bier and Planet found that extracts of rabbit's skin, which is comparatively rich in histamine, gave a positive test, while extracts of other rabbit tissues, which are poor in histamine, gave negative tests, it appeared probable that the capillary permeability factor in normal tissues might be histamine rather than some unknown specific tissue constituent. To test this possibility further, extracts from a variety of tissues have been examined with respect to their ability to give a trypan blue test and with respect to their histamine content. Method. Simple extracts were prepared by grinding 2 to 4 grams of tissue with sand in saline. The amount of saline was varied in different experiments, so that extracts of varying activity could be studied. The extracts were filtered and assayed for their histamine-equivalent content, using the isolated atropinized intestinal strip of the guinea pig for the assay. A solution of histamine acid phosphate of the same activity as the extract was prepared and both extract and histamine solution were injected into the abdominal skin of previously shaved rabbits.