Figure 5. JWU-A021 promotes Ca²⁺ influx rather than Ca²⁺ mobilization.

(a) The Ca²⁺ channel blocker La³⁺ exerted a concentration-dependent action to abrogate the increase of [Ca²⁺]_i stimulated by JWU-A021 (1 μM). (b) The action of JWU-A021 (1 μM) to increase [Ca²⁺]_i was abrogated when the Ca²⁺ concentration of the SES was reduced to 100 nM. (c,d) ATP dose-dependently increased the [Ca²⁺]_i measured under conditions in which the SES contained either 2.6 mM CaCl₂ (c) or 100 nM CaCl₂ (d). (e) The L-type Ca²⁺ channel blocker nimodipine (5 μM) slowed the rate of onset but failed to reduce the end-point increase of [Ca²⁺]_i measured in response to JWU-A021 (1 μM). (f) The effectiveness of nimodipine (5 μM) as an inhibitor of Ca²⁺ influx was demonstrated by its ability to fully block the end-point increase of [Ca²⁺]_i measured in response to 28 mM KCl-induced depolarization. For all examples depicted here, the findings are representative of a single experiment repeated a minimum of three times on three different occasions with similar results.