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

研究成果: Article

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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.

元の言語English
ページ(範囲)593-598
ページ数6
ジャーナルCardiovascular Drugs and Therapy
7
発行部数3 Supplement
DOI
出版物ステータスPublished - 1993 8 1
外部発表Yes

ASJC Scopus subject areas

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

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