Figure 4.

Non-linear interactions between Ca²⁺ influx and Ca²⁺ release during [cAMP] increases. Testing applications of 50 mM K⁺ and 100 μM ATP were made as indicated by horizontal bars. Changes in [Ca²⁺]_i and [cAMP]_i are shown by grey and black traces, respectively. The experiments were performed in control (left) and repeated 20 min after pretreatment with protein kinase A inhibitor H-89 (10 μM, right). A – Two depolarisation with high K⁺. B – Ca²⁺ release from ER with following depolarisation. C – Depolarisation and Ca²⁺ release. Note that potentiation of [cAMP] increases during the second treatments was abolished by H-89.