Figure 3

Interrelationships between calcium and cAMP transients measured with fura-2 and Epac-1-camps. Cytoplasmic calcium and cAMP (grey and black traces, respectively) were recorded with fura-2 and Epac-1-camps during testing challenges to 50 mM K⁺ and 1 mM ATP as indicated. Mean peak responses are given in Table 2. The applications were made in control (A) and then in the presence of 0.1 mM DDA (B) and 50 μM IBMX (C) to inhibit the activity of adenylate cyclase and phosphodiesterase, respectively. Note the changes in the amplitude of both calcium and cAMP transients after the treatments. The two panels in (D) show the responses in [Ca²⁺]_i and [cAMP]_i which were recorded 10 min after preincubation with 1 μM thapsigargin to deplete calcium stores (left) and in Ca²⁺-free solution to inhibit calcium influx (right).