Die invloed van toksiene van die skerpioenfamilies Buthidae en Scorpionidae op die ioonkanale van die rothart

Abstract

From observed clinical symptoms in several case studies over a few years it seems that the venom of scorpions from the Buthidae family are more potent than venom of scorpions from the Scorpionidae family. It was commonly thought that the differences in toxicity between the venoms of these two families could be explained due to the presence of different active chemical components in the whole venoms that influence different physiological mechanisms. The larger toxicity of the genus Parabuthus may be due to the presence of a specific component or fraction that is only present in smaller quantities or not present at all in the venom of Opithoptalmus. Differences in toxicity between the families may this be due to the activity of fraction 17. The active fractions of the venoms of Parabuthus villosus and 0pisthoptalmus carinatus were isolated by gelfiltration chromatography. The effects of the whole venoms and the different active fractions of the whole venoms on sodium channel activity and background currents of rat ventricular myocytes were studied by making use of voltage clamping with a single electrode in a whole cell setup. The whole venom of P. villosus as well as most of the active fractions from the venom prolongs the time duration of the inactivation phase of sodium channels dramatically and gives rise to incomplete inactivation of the sodium currents, typical a-toxin effects. After myocytes were treated with the venom of 0 . carinatus the ion currents at a holding potential of -1 00m V were shifted in an inward direction. Fraction 15 of the venom of 0. carinatus was the only identified fraction to cause similar effects as those that were observed with the whole venom. This perceptible shift of the ion currents is most probable the result of the forming of pores in the myocyte membranes through which non-selective ion flow occurs. These effects display characteristics that are partly similar to those of certain ionoforic effects. Fractions 11 and 20 of 0. carinatus give rise to typical a-toxin effects when myocytes are treated with these fractions. These effects were however outclassed in the whole venom by the effects of fraction 15. Several differences in the composition and effects of the venoms of the two different species were identified. The presence of these differences are related to the differences in feeding behavior and other factors that contribute to the phylogenetic selection of the species and can be traced to the differences in toxicity between the scorpion species and families. The antivenin currently available is produced from the venom of specie, Parabuthus transvaalicus. This study showed that this antivenin is effective for the suppression of the a-toxin effects on myocyte level caused by fraction 11 and 20 of the venom of 0. carinatus. This signifies certain similarities that may exist between the chemical structures of different fractions of the venoms of different scorpion families and that certain parts of the polypeptide structures of the different fractions of different scorpion species and families are identical.