“…This doubling of counterion concentration causes an increase in osmotic pressure together with swelling of mucin. It has been proposed that this yields the fully expanded MUC5B mucus gel on secretion (Kesimer, Makhov, Griffith, Verdugo, & Sheehan, ; Verdugo, ) although this remains a controversial issue (Ambort, ; Konturek, Bilski, Tasler, & Cieszkowski, ; Verdugo, ). A role for bicarbonate in the exchange of calcium ions has been demonstrated (Chen, Yang, Quinton, & Chin, ; Cooper, Quinton, & Ballard, ; Quinton, ) and linked with the CFTR channel (Gustafsson et al, ).…”