PMID: 8962709Nov 1, 1995Paper

The voltage dependence of contraction at different stimulation rates in guinea-pig ventricular myocytes

Experimental Physiology
S M Harrison

Abstract

Ventricular myocytes, isolated from the guinea-pig, were stimulated to contract by 100 ms long voltage clamp pulses from -80 to 0 mV at 0.5 and 3 Hz. An increase in frequency from 0.5 to 3 Hz led to a positive inotropic effect. Contraction-voltage relationships (CVR) were determined at each frequency. The CVR at 0.5 Hz was bell shaped and peaked between 0 and +20 mV, displaying a voltage dependence similar to the L-type Ca2+ current (ICa). At 3 Hz, contractions continued to increase at positive voltages, giving a more sigmoidal CVR. At 0.5 Hz, TTX reduced the size of steady-state contractions to 91 +/- 2% of control values, but had no effect on the shape of the CVR. At 3 Hz, TTX significantly reduced (P < 0.05) the magnitude of contractions at positive voltages (> or = +20 mV) but had no significant effect on contractions at voltages negative to 0 mV. These data illustrate that intracellular sodium activity (aNa(i)) and, in particular, Na+ entry due to the sodium current (INa) are important in determining the voltage dependence of contraction at positive voltages. Thapsigargin (2.5 microM), a blocker of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, reduced the size of steady-state contractions at 0 mV to 65 +/- 7% at 0.5 Hz. I...Continue Reading

Citations

Aug 10, 2000·European Journal of Biochemistry·R L McDonaldS M Harrison
Jul 4, 2007·The Veterinary Clinics of North America. Food Animal Practice·Richard Avery Zinn, Alejandro Plascencia Jorquera
Oct 8, 2017·Circulation. Cardiovascular Genetics·Jodie InglesBirgit Funke
Oct 8, 2017·Circulation. Cardiovascular Genetics·Aisha FurqanUNKNOWN SHaRe Consortium
Oct 2, 2007·American Journal of Physiology. Heart and Circulatory Physiology·Jonathan M CordeiroJ Andrew Wasserstrom

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