[Effect of angiotensin II and its receptor antagonist on electrophysiology and L-type calcium current in guinea cardiac myocytes].
OBJECTIVE
To evaluate the effect of angiotensin II (Ang II) and its receptor antagonist on action potential duration and L-type calcium current density of cardiac myocytes.


METHODS
Single myocyte of the ventricle in guinea was isolated. Action potentials were recorded using a conventional glass microelectrode filled with 3 mol/L KCl solution. Membrane patch clamp whole cell recording technique was used to investigate L-type calcium current maximum in holding potential of -40 mV, length of time 200 ms, command potential 0 mV.


RESULTS
Ang II induced arrhythmia of multiple electrophysiologic mechanisms. Action potential amplitude, 90% of action potential duration (APD90), and resting membrane potential (RMP) were significantly decreased or shortened after being perfused Ang II for 1 minute compared with controls. 30% of action potential duration (APD30), 50% of action potential duration (APD50), effective refractory period (ERP) were also shortened significantly after perfused Ang II for 3 minutes compared with controls. Ang II increased the L-type calcium maximum current density after a perfusion of 5 minutes, but losartan perfusion for 1 minute decreased the L-type calcium maximum current density, and it further decreased after perfusion for 3 minutes. However, the current voltage relationship curve was unchanged.


CONCLUSIONS
Ang II could decrease amplitude of monophasic action potential, rest membrane potential, shorten duration of monophasic action potential and effective refractory period, increase maximum current density of voltage dependent L-type calcium, and possess the effect of inducing arrhythmia. Losartan decreased maximum current density of voltage dependent L-type calcium.
Xu
Yan-min
YM
Department of Cardiology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China. xuyanmin@eyou.com
Huang
Ti-gang
TG
Chen
Yuan-lu
YL
D000200:Action Potentials / Q000187:drug effects; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D006168:Guinea Pigs; D019808:Losartan / Q000494:pharmacology*; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques
D020746:Calcium Channels, L-Type; D000804:Angiotensin II; D019808:Losartan