Figure 2.

Influence of db-cGMP (A), db-cAMP (B), 8-Br-cGMP (C), and 8-Br-cAMP (D) on Ca²⁺-dependent chemiluminescence of aequorin in protoplasts isolated from transgenic tobacco leaves and suspended in Ca²⁺-deficient medium (traces from chart recorder). The conditions of the experiments were the same as in Figure 1. E, Peak [Ca²⁺]_cyt values after the addition of cyclic mononucleotides and Ca²⁺ to protoplasts were calculated after chemiluminescence discharge under the action of 0.1% Triton X-100/100 mm CaCl₂ as described previously (Cobbold and Rink, 1987; Knight and Knight, 1995). Experiments were performed seven times; the error bars on histograms indicate sd.