Figure 6.

IK_Ca and SK_Ca regulate intracellular Ca²⁺ of resting endothelium in mesenteric arteries. (A) Perforated patch clamp was used to record membrane potential of Fluo-4–loaded endothelium to simultaneously measure changes in intracellular Ca²⁺. Time course graph illustrating the membrane potential and relative fluorescence of resting endothelium exposed to ChTX alone (black bars), with the addition of Ap (+Ap; white bars), and following the addition of 60 mM KCl (KCl; gray bars). (B) Voltage dependence of intracellular Ca²⁺ concentration from nonstimulated endothelium. Intracellular Ca²⁺ concentrations in each condition were estimated with Eq. 4 using [Ca²⁺]_Fo = 123 nM in the presence of 60 mM KCl (Knot et al., 1999) and associated with the corresponding membrane potential recorded. The value used for the K_d of Fluo-4 at 30°C was 370 nM (Woodruff et al., 2002). Solid line was fitted to data with the function Y = A*exp(−x/t) + B, where B = 120 ± 1 nM, A = 0.9 ± 0.4, and t = 13 ± 2.