FIGURE 6.

Depolarization induced cAMP uptake. (A) I_m recorded from a HeLaCx43/SpIH cell during perfusion with Ca²⁺-free NaCl solution containing 500 μM cAMP. Initially the cell was held at V_h = 0 mV (not shown in the record). There was a weak (~1.3-fold) current increase over approximately 80 s when the cell was held at V_h = +50 mV. Further cell membrane depolarization to V_h = +80 mV at ~80 s significantly enhanced the SpIH current in a time dependent manner by ~threefold (when adjusted to the same V_h). (B) SpIH current recorded in a HeLaCx43/SpIH cell during perfusion with Ca²⁺-free KAsp solution. The SpIH current increase was associated with the time-dependent membrane current increase during depolarization (noted by a red circle), typical of hemichannel activity.