Aortic response to adrenergic stimulation. Aortic constriction to noradrenaline (NA, 10 μM) was assessed for WT (open bars, N=17), CFTR-null (black bars, N=13), and dF piglets (gray bars, N=6) incubated in either PSS buffer alone or calcium-free buffer with EGTA. Aorta from dF piglets had decreased constriction during the 90 minute incubation, regardless of NA addition 30 minutes prior to study completion. Elimination of extracelluar calcium eliminated the heightened tone of WT and CFTR-null aorta. *P<0.05 versus WT, ‡P<0.01 or †P<0.05 for NA versus buffer, #P<0.05 for NA versus EGTA-NA.