Table 2.

Inhibition of calcium influx through voltage-dependent L-type calcium channels in GH₄C₁ cells by DHPs: comparison to inhibition of SOC channels in HL-60 cells

Compound	R1	R2	R3	R4	R5	R6	L-type channel		SOC channel IC50c (μM)	Ratio SOC/L-type
							Imaxa (%)	IC50b (μM)
1	H	Me	COOEt	Ph	COOMe	Me	54	0.01	40 ± 8	4000
2	H	Me	COOEt	CH=CH–Ph	COOMe	Me	40	1	15 ± 6	15
6d	H	Me	COOEt	3-NO2–Ph	COOMe	Me	92 ± 4	0.003 ± 0.001	3.3 ± 1.2	1100
7	H	Me	COOEt	3-NO2–Ph	COOEt	Me	77	0.003	5.0 ± 2.1	1600
8e	H	Me	COOMe	2-NO2–Ph	COOMe	Me	85 ± 3	0.01 ± 0.005	16 ± 2	1600
13	H	Me	COOEt	4-OMe–Ph	COOMe	Me	60	3	36 ± 3	12
20	H	Me	COOEt	3-NO2–Ph	COOCH2Ph	Me	55	0.001	1.8 ± 0.1	1800
21	H	Me	COOCH2Ph	3-NO2–Ph	COOCH2Ph	Me	60	0.001	3.0 ± 1.5	3000
30	Me	Me	COOMe	3-NO2–Ph	COOMe	Me	70	2	2.8 ± 0.3	1.4
32	Me	Me	COOEt	3-NO2–Ph	COOMe	Me	86 ± 7	1.3 ± 0.3	2.6 ± 1.1	2.0
33	Et	Me	COOEt	3-NO2–Ph	COOMe	Me	82 ± 4	2.3 ± 0.4	6	2.6
34	Allyl	Me	COOEt	3-NO2–Ph	COOMe	Me	72 ± 5	3.8 ± 1.8	6.8 ± 1.8	1.8
35	Propargyl	Me	COOEt	3-NO2–Ph	COOMe	Me	86 ± 7	2.1 ± 0.2	1.7 ± 1.3	0.8

^aI_max represents the maximum mean inhibition ± SEM (N = 3) by the DHP of the elevation of calcium levels elicited by depolarization of the cell membrane with 40 mM KCl. Single values are the average of two determinations.

^bThe IC₅₀ values represent the mean concentration ± SEM (N = 3) required for 50% of the maximum inhibition observed for each compound. Single values are the average of two determinations.

^cThe IC₅₀ values are from Table 1.

^dNitrendipine.

^eNifedipine.