Caffeine exerts a dual effect on capacitative calcium entry in Xenopus oocytes

Caffeine increases the amplitude of the Cl- currents evoked by capacitative Ca2+ entry (CCE) on thapsigargin-treated Xenopus oocytes. The caffeine-induced potentiation of the CCE process appears to rest on two distinct and additive components. The first component involves the cAMP second messenger system since it can be mimicked by either IBMX perfusion or cAMP microinjection into the oocyte and inhibited by the PKA inhibitory peptide i-PKA. The second component, although activatory, is dynamically related to the caffeine-evoked inhibition of InsP3-mediated Ca+ release and may arise from an interaction between caffeine and the InsP3 receptor in the context of a conformational coupling between the InsP, receptor and the channels responsible for CCE.