Rubescenslysin, a haemolytic protein from Amanita rubescens, disrupted the cytoplasmic membrane of human leucocytes which were more sensitive than erythrocytes. In the isolated hearts of rats and guinea pigs it caused systolic contracture, which was preceded by potassium outflow and sometimes by a transient positive inotropic effect. On the electrically stimulated guinea-pig left atrium it showed at first a positive, followed by a negative inotropic effect; on the spontaneously beating right atrium it produced transient positive followed by negative inotropic and chronotropic effects. Atria were less sensitive than intact hearts. In the isolated rat phrenic nerve-diaphragm preparation it produced a contracture, which was associated with reduction of indirect and direct contractility. In the isolated guinea-pig ileum it produced a slow contraction followed by tachyphylaxis. As excitability declined due to rubescenslysin, so did excitability by acetylcholine and potassium. Atropine and pheniramine had only feeble antagonistic effects, but papaverine was more powerful. In isolated rat hepatocytes, rubescenslysin caused a rapid outflow of potassium and coarse cell protrusions while later the cells became stainable with trypan blue. In the isolated perfused rat liver it produced a rapid outflow of potassium and of cytoplasmic and mitochondrial enzymes, and a somewhat slower outflow of lysosomal β-glucuronidase, accompanied by a rise in the lactate/pyruvate ratio and a decrease in bile production. In the isolated perfused rat kidney it caused an outflow of cytoplasmic and mitochondrial enzymes, together with massive proteinuria and serious restriction of sodium and potassium reabsorption and of urine output. In all the tissues investigated the effects of rubescenslysin began within a few min, were dose-dependent and practically irreversible. There were only minor differences in sensitivity between various organs and species. The observations indicate that the toxin is relatively nonspecific in its attack on components of cell membranes. © 1982.
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