Table 1

Comparative effects of Pb^2⁺ on various parameters in different recombinant Ca^2⁺ channel subtypes

	α_1C	α_1B	α_1E
IC₅₀(μM)	0.38	1.31	0.10
Activation curve	No effect	No effect	No effect
Inactivation curve	No effect	Negative shift	Negative shift
Reversibility	>90%	>90%	∼︀70%
Inactivation	Increase	Increase	Increase

α_2δand β subunits were used for all studies. 20 mM Ba^2⁺ was the charge carrier. Pb^2⁺ was applied extracellularly by continuous bath superfusion. Reversibility was tested using a 3-min wash with Pb^2⁺-free physiological saline after 1-min exposure to a concentration that approximated the relative IC₅₀ for that channel subtype.