Table 1. Luminal Ca²⁺ sensitivity in the presence of 10 µM cytoplasmic Ca²⁺ with 5 µM MgATP and reducing cytoplasmic redox potential.

P_o in all six channels at +40 mV and −40 mV; (1) fell with the addition of 5 mM MgATP (1 mM free Mg²⁺), (2) did not change consistently after the addition of redox buffers, (3) increased when luminal [Ca²⁺] was lowered to 0.1 mM, (4) was lower with 1.0 mM and 1.5 mM luminal Ca²⁺ than it had been with 0.1 mM luminal Ca²⁺.

^*Significantly less than mean P_o with 0.1 mM luminal Ca²⁺ (P<0.05).

^#Significantly greater than mean P_o under previous measurement with 1.0 mM luminal Ca²⁺ (P<0.05).

^$Significantly less than mean control P_o (P<0.05).