title: Potassium outward currents in freshly dissociated rabbit corpus cavernosum myocytes.
abstract: OBJECTIVE
  Cavernous smooth muscle cells have a key role in the control of penile erection and detumescence. In this study the types of smooth muscle cells and currents present in isolated rabbit corpus cavernosum myocytes were characterized.
  
  
  METHODS
  Immunohistochemical methods were used to identify cavernous smooth muscle cells. Currents were recorded from freshly dissociated myocytes using the whole cell and amphotericin perforated patch clamp techniques.
  
  
  RESULTS
  Cavernous myocytes were identified by alpha-smooth muscle actin and smooth muscle myosin immunoreactivity. Based on electrical properties at least 2 types of myocytes were present. Type I cells showed more depolarized membrane potentials, lower capacitance, higher input resistance and increased current densities at positive potentials than type II cells. In types I and II cells at voltages positive to 30 mV, maxi K+ channel (Ca2+ activated large conductance K+ channel or BK) blockade with iberiotoxin or charybdotoxin reduced outward currents by approximately 40% to 80% at 80 mV. Maxi K+ channel blocking did not affect cell membrane potential. Type II cells showed delayed rectifier K+ channel-type outward currents that were not detected in type I cells. Delayed rectifier K+ channel-type currents were resistant to iberiotoxin or charybdotoxin, activated at approximately -50 to -40 mV. and inactivated weakly.
  
  
  CONCLUSIONS
  The data suggest that cavernous smooth muscle cells are heterogeneous with at least 2 subtypes identified based on membrane potential, capacitance, input resistance, current density and delayed rectifier K+ channel expression. The activation threshold suggests that delayed rectifier K+ channels are open at the resting membrane potential and, therefore, contribute to control and regulation of the cavernous myocyte excitability.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Foundation/Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: J
authors.initials: J
authors.lastname: Malysz
authors.forename: S J
authors.initials: SJ
authors.lastname: Gibbons
authors.forename: S M
authors.initials: SM
authors.lastname: Miller
authors.forename: M
authors.initials: M
authors.lastname: Gettman
authors.forename: A
authors.initials: A
authors.lastname: Nehra
authors.forename: J H
authors.initials: JH
authors.lastname: Szurszewski
authors.forename: G
authors.initials: G
authors.lastname: Farrugia
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018999:Charybdotoxin / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects; D010413:Penis / Q000166:cytology*; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D014118:Toxins, Biological / Q000494:pharmacology
chemical_list: D010455:Peptides; D015221:Potassium Channels; D014118:Toxins, Biological; D018999:Charybdotoxin; C064719:iberiotoxin; D011188:Potassium