RESUMO
Experiments have been carried out to find potent inhibitors of hyaluronidases of Naja kaouthia (NK) and Calloselasma rhodostoma (CR) venoms with the aim of reducing local tissue damage and systemic toxicities caused by the venoms. Seven drugs/chemicals known to inhibit hyaluronidases were tested for their activity on venom enzymes. These were: sodium cromoglycate (SC), sodium aurothiomalate (SAT), apigenin, kaemferol, phenylbutazone, oxyphenbutazone and fenoprofen. The results showed that SC or SAT at 10 mM, completely inhibited the enzymes of both venoms. In in vivo experiments, SC or SAT, when incubated with NK venom prior to injection, significantly reduced edema and myonecrosis. In the case of CR venom, hemorrhage, in addition to edema and myonecrosis, was also significantly reduced. In the independent type experiment, SC or SAT were effective if injected within 1 min after the injection of venom. At longer time intervals of 3 and 10 min the inhibitors were effective in reducing some parameters of local tissue necrosis but the extent of inhibition was lower. SC and SAT at 256 and 195 microg/mouse, respectively, significantly prolonged the survival time of mice receiving lethal doses of NK. In the case of CR venoms, the two inhibitors not only prolonged the survival time but also prevented death of mice receiving lethal doses of the venom. The other inhibitors were poorly soluble in water and were studied only on enzyme inhibition and prolongation of survival time; they were mostly ineffective. Thus, SC and SAT when injected immediately at the sites of bites can reduce the systemic and local toxicity of NK and CR venoms. These results suggest that administration of these drugs at the site of venom injection may be useful in reducing venom-induced local tissue damage.
