Activation and reactivation of the ATP-sensitive K+ channel of the heart can be modified by drugs

Masayasu Hiraoka, Zheng Fan, Tetsushi Furukawa, Keiko Nakayama, Tohru Sawanobori

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Activation and reactivation of the ATP-sensitive K+ channel (IK.ATP) were studied with the patch-clamp technique in guinea-pig ventricular myocytes. The K+ channel openers, nicorandil and pinacidil, activated IK.ATP in an internal ATP-dependent manner. Both drugs increased the open probability of IK.ATP without changing the channel conductance. They prolonged lifetimes of bursts and shortened interburst intervals without influencing the fast gating within bursts. These effects were the opposite of those of internal ATP. However, the interaction between ATP and either nicorandil or pinacidil appeared not to be simple competition. We found that three carbonyl compounds-3,4-dihydroxybenzaldehyde, 2, 3-dihydroxybenzaldehyde, and 2,4-dihydroxyacetophenone-could activate IK.ATP through an intracellular mechanism that was dependent upon the presence of ADP and Mg2+. It has been suggested that these three carbonyl compounds bind covalently to proteins to form a Schiff base, which may be responsible for their effects upon IK.ATP. Internal application of the proteolytic enzyme trypsin prevented both the spontaneous and Ca2+-induced rundown of the KK.ATP channel. Tryptic digestion did not change either the channel's sensitivity to inhibition by ATP nor the fast gating kinetics of IK.ATP. Internal application of an exopeptidase, carboxypeptidase A, but not leuaminopeptidase, prevented the spontaneous and Ca2+-induced rundown of the IK/ATP channel, effects similar to those of trypsin treatment. These results suggest that the target site of trypsin digestion may be located on the carboxy (C)-terminal of the channel proteins or associated regulatory units.

Original languageEnglish (US)
Pages (from-to)593-598
Number of pages6
JournalCardiovascular Drugs and Therapy
Volume7
Issue number3 Supplement
DOIs
StatePublished - Aug 1 1993
Externally publishedYes

Fingerprint

Adenosine Triphosphate
Pharmaceutical Preparations
Pinacidil
Nicorandil
Trypsin
Digestion
Exopeptidases
Carboxypeptidases A
Schiff Bases
Patch-Clamp Techniques
Adenosine Diphosphate
Muscle Cells
Guinea Pigs
Proteins
Peptide Hydrolases

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Cardiology and Cardiovascular Medicine
  • Pharmacology (medical)

Cite this

Activation and reactivation of the ATP-sensitive K+ channel of the heart can be modified by drugs. / Hiraoka, Masayasu; Fan, Zheng; Furukawa, Tetsushi; Nakayama, Keiko; Sawanobori, Tohru.

In: Cardiovascular Drugs and Therapy, Vol. 7, No. 3 Supplement, 01.08.1993, p. 593-598.

Research output: Contribution to journalArticle

Hiraoka, Masayasu ; Fan, Zheng ; Furukawa, Tetsushi ; Nakayama, Keiko ; Sawanobori, Tohru. / Activation and reactivation of the ATP-sensitive K+ channel of the heart can be modified by drugs. In: Cardiovascular Drugs and Therapy. 1993 ; Vol. 7, No. 3 Supplement. pp. 593-598.
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