D110H-CFTR channels exhibited reduced mean burst durations but conductance levels similar to WT-CFTR. A: traces for WT-CFTR and D110H-CFTR activated by 1 mM ATP and 127 U/ml PKA. Recordings were made at Vm = −100 mV. c, Closed current level; o1, o2, and o3, open current levels for 1, 2, and 3 active channels in the patch. B: mean burst duration among D110 variants. *P < 0.05. Mean burst duration of charge-neutralized D110H-CFTR was similar to that of charge-sparing D110E-CFTR (reported in Ref. 8).