An increase in opening of BKCa channels in smooth muscle cells in streptozotocin-induced diabetic mice

AIM: To investigate the changes of function of large conductance of calcium-activated potassium channels (BKCa channels) in thoracic aortic smooth muscle cells in early stage of streptozotocin (STZ)-induced diabetic C57BL/6J mice. METHODS: Vascular muscle tension in the isolated thoracic aortic rings of mice was compared, and the role of BKCa channels in relaxation of isolated mice thoracic aortic rings induced by acetylcholine (ACh) was determined.Meanwhile, single vascular smooth muscle cells (VSMCs) were isolated by collagenase, and BKCa currents were recorded by patch-clamp single channel recording technique in symmetric high potassium solution. RESULTS:Tetraethylammonium (TEA) 1 mmol/L, a selective calcium-activated potassium channel blocker, caused significant rightward shift in the concentration-response curves of ACh in the isolated thoracic aortic rings of diabetic mice and pD2 value of ACh-induced relaxation was decreased notably after TEA treatment [(6.3±0.4) vs (6.9±0.5), n=10 rings from 7 mice, P0.05]. Furthermore,conductance of BKCa channels in single thoracic aortic smooth muscle cells was decreased [(199±15) pS, n=10 cells from 7 mice vs (266±11) pS, n=12 cells from 6 mice, P