CHARACTERIZATION OF THE MECHANISM OF ACTION OF NAJA OXIANA EICHWALD POISON FRACTIONS ON CARDIAC AND SMOOTH MUSCLE CONTRACTILE ACTIVITY.

Abstract

A dose-dependent effect of naja oxiana eichwald venom S-6 and S-7 fractions on cardiac muscle contractile activity was investigated, and it was found that they have a negative inotropic effect on muscle contraction force. S-6 fraction at a concentration of 2 μg/ml was observed to reduce cardiac muscle contraction force to 8.3±3.4% and S-7 fraction to 26.1±3.4% at 5 μg/ml. The suppressive effect of these fractions was maintained in the presence of nifedipine, but to a slightly lesser extent due to the blockade of Ca2+-channels accompanied by a decrease in the level of [Ca2+]i ions in cardiomyocytes. Blockade of Na+ channels with lidocaine also led to a noticeable suppression of the negative inotropic effect for fractions S-6 to 36.3±4.2% and S-7 to 41.6±4.4% of the control, respectively. Also, it was found that the effects of S-6 and S-7 fractions on rat aorta smooth muscle contraction strength were investigated. Considering that KCl-induced contractions of the rat aorta are mainly ensured by the activation of voltage-dependent Ca2+-channels, the observed effect of fractions S6 and S7 may be associated with inhibition of Ca2+ ion transport through these channels. The influence of fractions S6 and S7 of cobra venom on the functioning of voltage- and receptor-dependent Ca2+-channels in the rat aorta and cardiac muscle was studied.