Cytoplasmic trypsin-treatment of voltagesensitive potassium channels has been shown to cleave domains of the channel responsible for inactivation of the channel. Trypsin has also been reported to remove slow, irreversible inactivation, or run-down in ATP-sensitive potassium (KATP) channels. Cytoplasmic treatment of rat ventricular KATP channels with either crude, or pure trypsin (1-2 mg/ml) failed to prevent a slow run-down of channel activity. However, trypsin (porcine pancreatic type IX, or type II (Sigma Chem. Co.), or αchymotrypsin (Sigma Chem. Co.) rapidly and irreversibly removed, or substantially decreased glibenclamide and tolbutamide-sensitivity of the channels without removing sensitivity to ATP. We conclude that glibenclamide must bind to either a separate protein, or to a separate domain on the channel in order to effect channel inhibition, and this domain is functionally disconnected from the channel by trypsin-, or α-chymotrypsin treatment.

Original languageEnglish
Pages (from-to)617-619
Number of pages3
JournalPflügers Archiv European Journal of Physiology
Issue number6
StatePublished - Mar 1993


  • Adenosine triphosphate
  • Cardiac ventricle
  • Chymotrypsin
  • Glibenclamide
  • Heart
  • Metabolism
  • Potassium channel
  • Sulfonylurea
  • Trypsin


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