Abstract: AimTo study the effects of emodin on intracellular calcium concentration (［Ca₂₊］i) and L-type calcium current of the single ventricular myocytes from guinea pig. MethodsEnzymatic dissociation was used to isolate single ventricular myocytes from adult guinea pig. They were loaded with Ca₂₊-sensitive fluorecent indicator Fluo-3/AM. ［Ca₂₊］i represented by fluorescent intensity (FI) was measured by laser scanning confocal microscope. Whole cell patch clamp technique was used to record ICa-L. ResultsAt resting status, ［Ca₂₊］i was not affected by emodin (1-100 μmol·L^-1). Emodin at the concentration of 1 μmol·L^-1 was shown to increase the ［Ca₂₊］i induced by 60 mmol·L^-1 KCl. The peak value of fluorescent intensity was increased from 1 877±551 to 2 905±739 (n=8, P<0.05). Emodin at the concentration of 10 μmol·L^-1 had no effect on the increase of ［Ca₂₊］i induced by 60 mmol·L^-1 KCl. However, the increase of ［Ca₂₊］i induced by KCl was reduced to 1 214±335 (n=8, P<0.05) by 100 μmol·L^-1 emodin. The density of ICa-L was increased from (-6.2±1.3) pA/pF to (-8.3±0.3) pA/pF (n=6, P<0.05) by 1 μmol·L^-1 emodin at the test pulse of 0 mV. The current was not altered by 10 μmol·L^-1 emodin. But it was inhibited from (-6.6±1.0) pA/pF to (-3.80±0.16) pA/pF (n=6, P<0.05) by 100 μmol·L^-1 emodin at the test pulse of +10 mV. ConclusionEmodin has two-way regulation on ［Ca₂₊］i and ICa-L of cardiomyocytes in guinea pig.