Expression of T-type Ca(2+) channels in ventricular cells from hypertrophied rat hearts.
In this study we examined the existence of T-type Ca(2+) current in ventricular myocytes isolated from rats with pressure-overload hypertrophy. The whole-cell clamp technique was used to record Ca(2+) currents in enzymatically dissociated ventricular cells. T- and L-type Ca(2+) currents were separated by applying voltage steps to different test potentials from a holding potential of -80 mV and -50 mV. T-type Ca(2+) current was defined as the difference between the currents from the two holding potentials. Ventricular myocytes from sham-operated rats showed only L-type Ca(2+) current (maximal density -13.9+/-1.3 pA/pF n=17), whereas ventricular myocytes isolated from rats with aortic stenosis showed both L- and T-type Ca(2+) currents. The average values of T- and L-type Ca(2+) current density were -4.8+/-0.4 pA/pF and -12.4+/-0.9 pA/pF (n=32), respectively. T-type Ca(2+) current was distinguished from L-type Ca(2+) current by its voltage dependence, its kinetics and by its strong blockade by nickel 50 microM. In conclusion, we have demonstrated that hypertrophied ventricular rat cells express T-type Ca(2+) channels and this finding strongly supports a role for this channel in regulating growth processes in cardiac tissue.
Martínez
M L
ML
Institute of Pharmacology and Toxicology (CSIC-UCM), Universidad Complutense, Madrid, Spain.
Heredia
M P
MP
Delgado
C
C
D000818:Animals; D001024:Aortic Valve Stenosis / Q000503:physiopathology*; D015220:Calcium Channels / Q000502:physiology*; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D002478:Cells, Cultured; D006321:Heart / Q000503:physiopathology*; D006352:Heart Ventricles; D017379:Hypertrophy, Left Ventricular / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000473:pathology; D009532:Nickel / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D013779:Tetrodotoxin; D009532:Nickel