Ca++ dependence of histamine release and formation of slow reacting substance in the cat paw.

Abstract

AbstractThe influence of divalent cations on the release of histamine and the formation of slow reacting substance (SRS) in the perfused cat paw induced by compound 48/80 was studied. Ca++ was found to have a stimulatory effect on both processes. Ca++ had no releasing effects per se. When the paws were perfused for 1 or 2 hrs with Ca++‐free salt solution, prior to compound 48/80, the release was depressed. Histamine release and formation of SRS were inhibited by disodium ethylene diamine tetraacetate (EDTA). In both instances the EDTA‐blockade could be reversed by Ca++, whereas Ca++, Mg++, Mn++ and Ni++ were ineffective substitutes. The EDTA‐blockade of histamine release but not that of the formation of SRS was also reversed by Sr++ and in some experiments by Ba++. The stimulatory effect of Sr++ on the release of histamine was weaker than that of Ca++. No significant stimulatory effect of Sr++ on the formation of SRS was observed. It is concluded that the release of histamine and the formation of SRS in the cat paw are Ca++‐dependent processes although in the case of histamine release Ca++ can partially be replaced by Sr++.