Absorption and distribution of 131I-labeled cobra venom and its purified toxins

Abstract

The absorption and distribution of Formosan cobra ( Naja naja atra) venom and its purified toxins (neurotoxin and cardiotoxin) have been studied by using 131I-labeled preparations. Absorption of cardiotoxin, as well as the crude venom, after subcutaneous injection in mice was very slow; only about 30% of the injected cardiotoxin was absorbed within 4 hours. Absorption of neurotoxin was much faster, about 60% within 2 hours. Although small amounts of radioactivity could be detected in the cerebrospinal fluid (CSF) of rabbits injected intravenously with 1 mg per kilogram of the venom, neurotoxin, or cardiotoxin, the CSF levels were too low to account for the rapid respiratory paralysis caused by cobra venom or its neurotoxin. After intravenous injection in rabbits, the plasma level of cardiotoxin declined much more rapidly than that of neurotoxin. Cardiotoxin was taken up by various organs, especially by kidneys, liver, spleen, and lungs, whereas neurotoxin did not accumulate in any particular organs except in kidneys, where a high amount was found. The distribution patterns of these toxins given intravenously in mice were in general similar to those in rabbits. Radioautography shows that neurotoxin localized in the motor end-plate zone of the mouse diaphragm, whereas cardiotoxin spread widely over the whole diaphragm.