Mechanically activated currents in chick heart cells.
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.
Hu
H
H
Biophysical Sciences, 120 Cary Hall, SUNY at Buffalo, Buffalo, NY 14214, USA.
Sachs
F
F
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002642:Chick Embryo; D002712:Chlorides / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D007038:Hypotonic Solutions / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D011312:Pressure; D012964:Sodium / Q000502:physiology*; D013111:Spider Venoms / Q000494:pharmacology
D002712:Chlorides; D007038:Hypotonic Solutions; D007473:Ion Channels; D009498:Neurotoxins; D010456:Peptides, Cyclic; D013111:Spider Venoms; C082807:omega-grammotoxin SIA; D012964:Sodium; D005682:Gadolinium; D011188:Potassium; D002118:Calcium