title: Penitrem A as a tool for understanding the role of large conductance Ca(2+)/voltage-sensitive K(+) channels in vascular function.
abstract: Large conductance, Ca(2+)/voltage-sensitive K(+) channels (BK channels) are well characterized, but their physiological roles, often determined through pharmacological manipulation, are less clear. Iberiotoxin is considered the "gold standard" antagonist, but cost and membrane-impermeability limit its 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 its utility for studying vascular function in vitro and in vivo. Whole-cell currents from human embryonic kidney 293 cells transfected with hSlo α or α + β1 were blocked >95% by penitrem A (IC(50) 6.4 versus 64.4 nM; p < 0.05). Furthermore, 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(+) currents, cloned voltage-dependent Kv1.5 channels, or native ATP-dependent K(ATP) current. Penitrem A enhanced the 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 for studying the role of BK channels in vascular function and is practical for cell and tissue (in vitro) studies as well as anesthetized animal (in vivo) experiments.
authors.affiliation: Division of Exercise Physiology, Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine, Morgantown, West Virginia 26506, USA
authors.forename: Shinichi
authors.initials: S
authors.lastname: Asano
authors.forename: Ian N
authors.initials: IN
authors.lastname: Bratz
authors.forename: Zachary C
authors.initials: ZC
authors.lastname: Berwick
authors.forename: Ibra S
authors.initials: IS
authors.lastname: Fancher
authors.forename: Johnathan D
authors.initials: JD
authors.lastname: Tune
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Dick
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002461:Cell Line, Transformed; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D004285:Dogs; D057809:HEK293 Cells; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D009183:Mycotoxins / Q000494:pharmacology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D009183:Mycotoxins; D010455:Peptides; D010656:Phenylephrine; C003626:tremortin; C064719:iberiotoxin; D011188:Potassium