ACTIVATION BY METHYLENE-BLUE OF LARGE CA2-ACTIVATED K+ CHANNELS()

Using the patch-clamp method, we found that methylene blue (MB), a fre e radical inhibitor of guanylyl cyclase, activated large, Ca2+-activat ed K+ channels (BKCa) in either cell attached or excised, inside-out p atches of human mesangial cells in culture. Since BKCa are important f eedback regulators of contraction of smooth muscle and mesangial cells , these results indicate that MB may be an important opener of BKCa ch annels and a regulator of vascular volume and resistance.