Abstract
Large conductance, Ca2+/voltage-sensitive K+ (BK) channels are well characterized, but physiological roles, often determined through pharmacological manipulation, are less clear. Iberiotoxin is considered the "gold standard" antagonist, but cost and membrane-impermeability limit usefulness. Economical and membrane-permeable alternatives could facilitate the study of BK channels. Thus, we characterized the effect of penitrem A, a tremorigenic mycotoxin, on BK channels and demonstrate utility for studying vascular function in vitro and in vivo. Whole-cell currents from HEK 293 cells transfected with hSlo α or α + β1 were blocked >95% by penitrem A (IC50 6.4 vs. 64.4 nM; p<0.05). Further, penitrem A inhibited BK channels in inside-out and cell-attached patches, whereas iberiotoxin could not. Inhibitory effects of penitrem A on whole-cell K+ currents were equivalent to iberiotoxin in canine coronary smooth muscle cells. As for specificity, penitrem A had no effect on native delayed rectifier K+ current in canine coronary smooth muscle, cloned human KV1.5 channels, or pinacidil-induced relaxation of canine coronary arteries. Penitrem A enhanced sensitivity to K+-induced contraction in canine coronary arteries by 23 ± 5% (p<0.05) and increased the blood pressure response to phenylephrine in anesthetized mice by 36 ± 11% (p<0.05). Our data indicate that penitrem A is a useful tool to study the role of BK channels in vascular function and is practical for cell and tissue (in vitro) studies as well as anesthetized whole animal (in vivo) experiments.
- calcium-activated potassium channels
- potassium channels
- vascular smooth muscle
- voltage-gated potassium channels
- Received December 15, 2011.
- Revision received May 8, 2012.
- Accepted May 9, 2012.
- The American Society for Pharmacology and Experimental Therapeutics