Influence hydrogen sulfide on Ca2+-dependent potassium permeability of the membrane of human erythrocytes

The purpose of the research was to study the influence of hydrogen sulfide donor NaHS on red blood cells membrane potential changes caused by the activation of Ca2+ dependent K+ channels in the presence of calcium ionophore or artificial electron donor system ascorbate phenazine methosulfate. Materials and methods. We used the packed erythrocytes obtained from venous blood of 25 healthy volunteers at the age of 20-27 years. Registration of the membrane potential of erythrocytes in the presence of Ca2+ ionophore (A23187) or artificial electron donor system ascorbate - FMS was performed with potentiometric method based on the fact that in the presence of the protonophore distribution of H + depends on the membrane potential Em like as Em = RT/F (pH i - pH 0). Here pH i and pH 0 are pH of the incubation medium and cytoplasm, respectively. An amplitude of hyperpolarizing response (HR) was calculated as an integral characteristic of Ca2+-dependent permeability for K+. Results. The addition of NaHS at concentrations from 0.2 mM to 0.005 mM into the cells incubation medium caused a change in the amplitude of hyperpolarizing response of erythrocyte membranes induced by both methods. In the presence of 0.005 mM NaHS the amplitude of A23187-dependent HR increased significantly, whereas the amplitude of the redox-dependent HR decreased. Suppression of A23187-dependent HR in the presence of higher concentrations of NaHS was more pronounced than the suppression of the amplitude of redox-dependent response. The amplitude of A23187-dependent HR increased under the joint action of hydrogen sulfide and the blocker of Na+, K+, 2Cl(-)-cotransport (NKCC) bumetanide, and the amplitude of redox-dependent HR decreased in comparison with the parameters obtained in the absence of a blocker. Conclusion. It is found that hydrogen sulfide exerts a modulatory effect on K (Ca2+) -channels of erythrocyte membrane. The effect of H2S depends on the method of activation of the studied channels. A23187-dependent HR was more sensitive to H2S in comparison to redox-induced HR of erythrocyte membrane. The effect of NaHS on the amplitude of the HR in the presence of NKCC blocker bumetanide also depended on the method of stimulation of channels.