ABSTRACT
<p><b>AIM</b>To determine the effects of cyclovirobuxine D (CD) on intracellular Ca2+ mobilization and L-type Ca2+ current (I(Ca-L)) in isolated rat cardiomyocytes.</p><p><b>METHODS</b>The effects of CD on the amplitude of I(Ca-L) and intracellular Ca2+ mobilization induced by KCl and caffeine were studied with the method of patch-clamp technique and laser scanning confocal microscopy in rat ventricular myocytes.</p><p><b>RESULTS</b>CD decreased the amplitude of I(Ca-L) in a concentration-dependent manner. At 10 mV, 1 and 10 micromol x L(-1) CD decreased I(Ca-L) density from (- 9.9 +/- 1.8) pA/pF to (-6.4 +/- 1.4) and (-4.2 +/- 0.6) pA/pF, respectively. Confocal experiments showed that intracellular fluorescent intensity (FI) value of [Ca2+] in control resting level was not changed by 1 and 10 micromol x L(-1) CD. [Ca2+] increase in response to KCl could not be reduced by CD. The rise of [Ca2+]i in response to caffeine was further enhanced by pretreatment with CD.</p><p><b>CONCLUSION</b>CD decreased I(Ca,L) in a concentration-dependent manner and increased [Ca2+]i release induced by caffeine in rat ventricular cardiomyocytes.</p>
Subject(s)
Animals , Female , Male , Rats , Buxus , Chemistry , Calcium , Metabolism , Calcium Channels, L-Type , Cell Separation , Drugs, Chinese Herbal , Pharmacology , Heart Ventricles , Cell Biology , Myocytes, Cardiac , Metabolism , Plants, Medicinal , Chemistry , Rats, WistarABSTRACT
<p><b>AIM</b>To clarify mechanisms that the antiarrhythmic effects of matrine and berbamine are weaker than those of amiodarone and RP58866.</p><p><b>METHODS</b>Experimental arrhythmic models were induced by aconitine, coronary artery ligation and electric stimulation in rats and rabbits. Whole-cell patch-clamp techniques were used to record IK1, IKr, IKs and Ito.</p><p><b>RESULTS</b>Matrine and berbamine significantly increased the dose of aconitine for induction of ventricular premature and ventricular tachycardia in rats, decreased the number of arrhythmias induced by coronary artery ligation in rats and increased ventricular fibrillation threshold (VFT) induced by electric stimulation in rabbits, but the anti-arrhythmic potency of matrine and berbamine was lower than that of amiodarone and RP58866. The inhibitory actions of matrine and berbamine on IK1, IKr, IKs, Ito were lower than those of amiodarone and RP58866. The IC50 of matrine for IK1, IKr, IKs, Ito were (46 +/- 3), (32.9 +/- 1.2), (37 +/- 8) and (7.6 +/- 0.5) mol x L(-1), respectively. The IC50 of amiodarone for IK1, IKr, IKs, Ito were (21 +/- 5) , (3.7 +/- 0.7), (5.9 +/- 0.9) and (5.9 +/- 0.6) mol x L(-1), respectively.</p><p><b>CONCLUSION</b>The inhibitory actions of matrine and berbamine on IK1, IKr, IKs, Ito were lower than those of amiodarone and RP58866, which might be the reason that the antiarrhythmic effects of matrine and berbamine were weaker than those of amiodarone and RP58866.</p>