PP.42.17: ROLE OF NKCC IN CONTRACTILE ACTION OF HYDROGEN SULFIDE ON VASCULAR SMOOTH MUSCLE CELLS. (June 2015) - Smaglii, L.
Abstract : Objective: Hydrogen sulfide (H2S) as a vasorelaxing agent is considered to be a potential antihypertensive drug. However, there is evidence that H2S at small concentrations causes constriction of blood vessels. The mechanisms of such action are still unclear. However, identification of these mechanisms will help to determine the additional physiological function of H2S in the regulation of vascular tone and to establish the possible side effects of H2S as a medicine. Design and method: The study was performed by method of mechanography using endothelium-denuded aortas smooth muscle segments (SMS) of male Wistar rats. Contractions were induced by highpotassium (30KCl) solution. The amplitude of contractile responses was calculated as a percentage of the control 30KCl- induced contraction. The activity of Na+, K+, 2Cl- - cotransporter (NKCC) was examined on freshly isolated aortas smooth muscle cells of male Wistar rats as a velocity of rubidium (86Rb+) entry by radionuclide method. Sodium hydrosulfide (NaHS) was used as a donor of H2S. Its solution was prepared immediately before use; the pH of the solution was maintained at the value of 7.35–7.40. Results: Mechanical tension (MT) of SMS precontracted with 30KCl was increased by NaHS (5–50 μM) to 109.1 ± 2.5%, 115.9 ± 3.4% and 118.5 ± 3.5% (n = 9, p < 0.05), respectively, from the control, but reduced by addition of 500–1000 μM NaHS to 64.9 ± 7.5% and 48.3 ± 5.0% (n = 9, p < 0.05), respectively. Inhibitor of NKCC bumetanide (100 μM) absolutely abolished the contractile effect of 5, 10, 50 NaHS (MT was 95, 9 ± 1, 2% (n = 5); 92, 1 ± 1, 9% (n = 7, p < 0, 05); 93, 6 ± 2, 8% (n = 5, p < 0, 05), respectively, from the control highpotassium contraction in the presence of bumetanide); relaxing action of bumetanide in concentrations of 100, 500, 1000 μM significantly increased: MT was 33, 8 ± 5, 8% (n = 6; p < 0, 05), 19, 0 ± 4, 0% (n = 5, p < 0, 05), 19, 0 ± 4, 0% (n = 5, p < 0, 05) respectively, from the control highpotassium contraction in the presence of bumetanide. Radionuclide study of NKCC activity showed a significantly increase in its activity under the action of 10, 50, 100 μM of NaHS, that was 127, 0 ± 8, 0 (n = 4, p < 0, 05), 146, 0 ± 7, 0% (n = 4, p < 0, 05) and 138, 0 ± 11, 0% (n = 4, p < 0, 05) from the control. Conclusions: Contractile action of H2S on smooth muscle cells precontracted with highpotassium solution is due to activation of NKCC.