Mechanically activated currents in chick heart cells

J Membr Biol. 1996 Dec;154(3):205-16. doi: 10.1007/s002329900145.

Abstract

As predicted from stretch-induced changes of rate and rhythm in the heart, acutely isolated embryonic chick heart cells exhibit whole-cell mechanosensitive currents. These currents were evoked by pressing on cells with a fire polished micropipette and measured through a perforated patch using a second pipette. The currents were carried by Na+ and K+ but not Cl-, and were independent of external Ca2+. The currents had linear I/V curves reversing at -16 mV and were completely blocked by Gd3+ >/= 30 microM and Grammostola spatulata venom at a dilution of 1:1000. Approximately 20% of cells showed time dependent inactivation. In contrast to direct mechanical stimulation, hypotonic volume stress produced an increase in conductance for anions rather than cations-the two stimuli are not equivalent. The cells had two types of stretch-activated ion channels (SACs): a 21 pS nonspecific cation-selective reversing at -2 mV and a 90 pS K+ selective reversing at -70 mV in normal saline. The activity of SACs was strongly correlated with the presence of whole-cell currents. Both the whole-cell currents and SACs were blocked by Gd3+ and by Grammostola spatulata spider venom. Mechanical stimulation of spontaneously active cells increased the beating rate and this effect was blocked by Gd3+. We conclude that physiologically active mechanosensitive currents arise from stretch activated ion channels.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials
  • Animals
  • Calcium / pharmacology
  • Chick Embryo
  • Chlorides / pharmacology
  • Gadolinium / pharmacology
  • Heart / drug effects
  • Heart / embryology
  • Heart / physiology*
  • Heart Rate / physiology
  • Hypotonic Solutions / pharmacology
  • Ion Channel Gating* / drug effects
  • Ion Channels / drug effects
  • Ion Channels / physiology*
  • Neurotoxins / pharmacology
  • Patch-Clamp Techniques
  • Peptides, Cyclic / pharmacology
  • Potassium / physiology*
  • Pressure
  • Sodium / physiology*
  • Spider Venoms / pharmacology

Substances

  • Chlorides
  • Hypotonic Solutions
  • Ion Channels
  • Neurotoxins
  • Peptides, Cyclic
  • Spider Venoms
  • omega-grammotoxin SIA
  • Sodium
  • Gadolinium
  • Potassium
  • Calcium