EFFECT OF TETRANDRINE ON CALCIUM CURRENT RECORDED BY PERFORATED PATCH RECORDING WITH BETA-ESCIN IN GUINEA PIG VENTRICULAR MYOCYTES

AIMTo record L-type calcium current (I_Ca,L) and T-type calcium current (I_Ca,T) by perforated patch recording technique with β-escin in isolated guinea pig ventricular myocytes, and to investigate the effect of tetrandrine (Tet) on I_Ca,L and I_Ca,T. METHODSSingle myocytes were dissociated by enzymatic dissociation method. I_Ca,L was recorded by perforated patch recording (PPR) and whole cell patch recording (WCR) techniques and I_Ca,T was recorded by PPR. RESULTS25 μmol·L^-1 β-escin was shown to permeate the myocytes membrane and obtain PPR mode with success rate of 94% (16/17). Run-down of I_Ca,L was considerably slower in PPR mode than in traditional WCR mode. Under PPR condition, 1～300 μmol·L^-1 Tet inhibited I_Ca,L in a concentration-dependent manner with an IC₅₀ value of (15±5) μmol·L^-1 (95% confidence area: 10.6～18.9 μmol·L^-1, N=6), 300 μmol·L^-1 Tet decreased I_Ca,L from (-15.1±2.6) pA·pF^-1 to (-3.3±1.1) pA·pF^-1, with an inhibition rate of (77±10)%, (P<0.01, N=6). 300 μmol·L^-1 Tet shifted the current-voltage relation (I～V) curves of I_Ca,L upwardly, but it did not change the steady state activation curves of I_Ca,L. The inhibition rate of 3, 30 and 300 μmol·L^-1 Tet on I_Ca,T were (16±5)%, (40±7)% and (75±11)% (P<0.01, N=6) respectively. CONCLUSIONUsing 25 μmol·L^-1 β-escin can easily obtain stable PPR mode in isolated guinea pig ventricular myocytes. Under PPR condition, Tet was found to inhibit I_Ca,L and I_Ca,T concentration dependently.