Effect of didrovaltrate on I-calcium current in rabbit ventricular myocytes

Objective: To investigate the effect of didrovaltrate on L-type calcium current (I(Ca-L)) in rabbit ventricular myocytes.

Methods: We used the whole cell patch clamp recording technique.

Results: Didrovaltrate at concentrations of 30 microg/ L and 100 microg/L significantly decreased peak I(Ca-L) (I(Ca-Lmax)) from (6.01 +/- 0.48) pA/pF to (3.45 +/- 0.27) pA/pF and (2.16 +/- 0.19) pA/pF (42.6% and 64.1%, n=8, P< 0.01), respectively. Didrovaltrate shifted upwards the current-voltage curves of I(Ca-L) without changing their active, peak and reverse potentials. Didrovaltrate affected the steady-state inactivation of I(Ca-L). The half activation potential (V1/2) was significantly shifted from (-26 +/- 2) to (-36 +/- 3) mV (n=6, P<0.05), with a significant change in the slope factor (k) (from 8.8 +/- 0.8 to 11.1 +/- 0.9, n=6, P<0.05). Didrovaltrate did not affect the activation curve.

Conclusion: Didrovaltrate blocks I(Ca-L) in a concentration-dependent manner and probably inhibits I(Ca-L) in its inactive state, which may contribute to its cardiovascular effect.