S- and P-type cobra venom cardiotoxins differ in their action on isolated rat heart

Abstract

Background: The cardiovascular system is one of the first systems to be affected by snake toxins; but not many toxins exert a direct effect on the heart. Cobra venom cardiotoxins are among those few toxins that attack the heart. Although the two cardiotoxin types (S and P) differ in their central-loop structure, it is not known whether they differ in their effect on the mammalian heart. We compared the effects of S-and P-type cardiotoxins, CTХ-1 and CTХ-2, respectively, from the cobra Naja oxiana, on the isolated rat heart. Methods: An isolated rat heart perfused according to the Langendorff technique was used in this study to investigate the activity of cardiotoxins CTX-1 and CTX-2. The following parameters were registered: the left ventricular developed pressure, calculated as the difference between systolic and diastolic pressure in the left ventricle, the end-diastolic pressure, the heart rate, time to maximal end-diastolic pressure (heart contracture), and time to depression of the heart contraction. Results: Both cardiotoxins at the concentration of 5 μg/mL initially produce a slight increase in systolic intraventricular pressure, followed by its rapid decrease with a simultaneous increase in diastolic intraventricular pressure until reaching contracture. CTX-2 blocks cardiac contractions faster than CTX-1; in its presence the maximum diastolic pressure is reached faster and the magnitude of the developed contracture is higher. Conclusion:The P-type cardiotoxin CTX-2 more strongly impairs rat heart functional activity than the S-type cardiotoxin CTX-1, as expressed in its faster blockage of cardiac contractions as well as in more rapid development and greater magnitude of contracture in its presence.

The Effects of Cobra Cardiotoxins on the Papillary Muscle and Langendorf Perfused Rat Heart Are Not Associated With Adrenaline Release

“…Кардиотоксины яда кобр представляют собой группу трехпетельных токсинов, общим свойством которых является прямое взаимодействие с клеточной мембраной, ведущее к образованию ионной поры, деполяризации, кальциевой перегрузке и как следствие гибели клетки. Нами проведено исследование кардиотоксинов 1 (КТ-1) и 2 (КТ-2) яда кобры Naja oxiana и показано, что КТ-2 заметно превосходит по своей активности КТ-1 при воздействии на препараты папиллярной мышцы и кольца грудной аорты крысы [1], а также на сердце крысы, перфузируемое по Лангендорфу [2]. КТ-1 и КТ-2 подобно другим кардиотоксинам давали временное увеличение силы сокращения [3,4].…”