Water and electrolytes of exocrine secretions. pp. 179-91.

It has been recognized that the levels of water and electrolytes are 
deranged in many, if not all, of the exocrine secretions of 
cystic fibrosis patients. The sodium and chloride levels in serous secretions 
from CF patients are elevated. In contrast, the more protein-rich or 
mucoid, isotonic secretions (viz, from the pancreas and tracheobronchial mucus glands) 
are found to have sodium concentrations near normal or even somewhat 
decreased. However, these secretions have significantly reduced water content. The abnormalities 
in hypotonic secretions appear to rise from a decreased Na+ reabsorption 
in the ducts. The low water content of the isotonic secretions 
of CF patients appears to result from decreased secretion of water 
and electrolytes. Early studies on tracheobronchial secretions from CF patients led 
investigators to suggest that the primary defect may be a decrease 
in the levels of water and monovalent ions. In an attempt 
to provide a unifying hypothesis, it has been suggested that an 
increased calcium concentration in the various exocrine secretions leads to a 
"hyperpermeability" of the mucus linings and thus to an excessive loss 
of water and small ions. The concentration of calcium in exocrine 
secretions appears to follow the concentration of proteins and especially the 
mucous glycoproteins. It was suggested that calcium may be an important 
factor in the increased viscosity and insolubility of CF mucus. Organic 
ions are also potential perturbants of macromolecular structure. In addition to 
a possible perturbant role, polyamines have a potential role in water 
and electrolyte transport. 