Changes of membrane currents in cardiac cells induced by long whole-cell recordings and tolbutamide

Pflugers Arch. 1987 Aug;409(6):582-8. doi: 10.1007/BF00584657.


Single isolated myocytes were obtained from the ventricles of adult guinea pig hearts. The whole-cell recording configuration of the patch-clamp technique was used to measure membrane currents. A decrease (run-down) of the Ca2+ inward current and an increase of a time-independent K+ outward current were observed during long lasting (1-3h) recordings. The time at which the outward current developed depended on the intracellular ATP concentration in the pipette, suggesting that this current is identical to the ATP-dependent K+ current described by Noma and Shibasaki (1985). However, the maximum outward current reached in the experiments was independent of the ATP concentration indicating a limited diffusion of ATP in the cell interior. In single-channel experiments on isolated patches of cell membrane and in whole-cell recordings the ATP-dependent K+ current could be blocked by the hypoglycaemic sulphonylurea tolbutamide. The IC50 of 0.38 mM was about 50 times higher than that reported for pancreatic beta-cells (Trube et al. 1986). The Ca2+ inward current and the inwardly rectifying K+ current were not affected by tolbutamide (3 mM).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Adenosine Triphosphate / antagonists & inhibitors*
  • Animals
  • Calcium / metabolism
  • Female
  • Guinea Pigs
  • Ion Channels / drug effects*
  • Male
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Potassium / metabolism*
  • Tolbutamide / pharmacology*


  • Ion Channels
  • Adenosine Triphosphate
  • Tolbutamide
  • Potassium
  • Calcium