CFTR and cystic fibrosis: Typical of CF jejunum in humans and in other CF animal models, forskolin-stimulated (Fsk-stimulated; MilliporeSigma) and bumetanide-inhibitable anion secretion (MilliporeSigma) were absent in CF rabbit jejunum at both younger and older ages (mean P52 [Figure 1D] and P367 [Supplemental Figure 3C]), consistent with loss of CFTR function (11, 31–36).