In vitro activity: Nisoldipine is a potent blocker of L-type calcium channels. Nisoldipine binds directly to inactive calcium channels stabilizing their inactive conformation Similar to other DHP CCBs. Nisoldipine displays selectivity for arterial smooth muscle cells due to great number of inactive channels and the α1 subunit of the channel. Nisoldipine is about 30 times less selective for delayed-rectifier K+ channels than for L-type Ca2+ channels, which inhibits IKr (rapidly activating delayed-rectifier K+ current) with IC50 of 23 μM, and IKs (slowly activating delayed-rectifier K+ current)with IC50 of 40 μM in guinea-pig ventricular myocytes. Nisoldipine also displays antioxidant potency with IC50 of 28.2 μM both before and after the addition of active oxygen. This is tested by means of rat myocardial membrane lipid peroxidation with a nonenzymatic active oxygen-generating system (DHF/FeC13-ADP).

Kinase Assay: CHO cells expressing the subunit of the voltage-dependent L-type Ca2+ channel are cultrured in medium without serum in the presence of different concentrations of Nisoldipine. Then Ca2+ channel current elicited from a holding potential of -100 mV or -50 mV is recorded at room temperature with the whole-cell configuration of the patch-clamp method using the List EPC-7 patch-clamp amplifer and pClamp software. The concentration of competitor inhibiting 50% of the specific binding represents IC50. 

Cell Assay: The myocytes are bathed in normal Tyrode's solution, held at -80 mV, and depolarised after 200-ms prepulses (-40mV) to more positive potentials for 500 ms at 0.1 Hz, tail currents are recorded on repolarisations to -40mV. The myocytes are exposed to 10-100 mM Nisoldipine for 8-10 minutes. Then the whole-cell membrane currents are recorded using an EPC-7 amplifier.