Trypsin and alpha-chymotrypsin treatment abolishes glibenclamide sensitivity of KATP channels in rat ventricular myocytes.
Cytoplasmic trypsin-treatment of voltage-sensitive 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 alpha-chymotrypsin (Sigma Chem. Co.) rapidly and irreversibly removed, or substantiallly 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 alpha-chymotrypsin treatment.
Nichols
C G
CG
Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, Mo 63110.
Lopatin
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AN
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002918:Chymotrypsin / Q000494:pharmacology*; D005905:Glyburide / Q000494:pharmacology*; D007700:Kinetics; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D014357:Trypsin / Q000494:pharmacology*
D015221:Potassium Channels; D000255:Adenosine Triphosphate; D002918:Chymotrypsin; D014357:Trypsin; D005905:Glyburide