Fig. 1

Voltage-dependent activation of a transient increase in fluo-3 Ca²⁺ transients in a normal parathyroid cell. Left Application of a 150 mM K⁺ solution (2 mM Ca²⁺) evoked a transient increase in fluo-3 fluorescence (Ca²⁺ transient). Right Application of a nominally Ca²⁺-free 150 mM K⁺ solution failed to increase fluo-3 fluorescence. F Baseline fluorescence, ∆F change in fluorescence in response to stimulation