Standardized assay for the sodium reabsorption inhibitory effect and studies of its salivary gland distribution in patients with cystic fibrosis.

The retrograde perfusion assay of Magos for the sodium reabsorption inhibitory effect 
in sweat and mixed saliva from patients with cystic fibrosis (CF) 
was modified by (1) using the second parotid gland of the 
rat as a control, (2) carefully controlling the quantity of saliva 
perfused into the rat parotid gland so that the ratio of 
milliliters perfused to gram dry gland weight fell between 1.8 and 
2.8, and (3) reporting the inhibitory effect as percentage of inhibition 
of the rate of sodium reabsorption (RNa) in the perfused gland 
calculated from the difference between the RNa's in the two glands. 
Using this modified assay we were able to confirm that significant 
differences exist in the percentage of inhibition of RNa caused by 
CF and normal mixed saliva (47.0 plus or minus 24.8 and 
18.0 plus or minus 8.3, mean plus or minus SD). In 
addition, similar significant differences in the percentage of inhibition of RNa 
by submandibular gland secretions (39.7 plus or minus 13.5 and 16.0 
plus or minus 11.8), sublingual gland secretions (39.5 plus or minus 
6.0 and 19.7 plus or minus 14.3), and submucosal gland secretions 
(34.0 plus or minus 11.7 and 21.7 plus or minus 12.7) 
between CF and normal subjects were observed. However, parotid gland secretions 
from CF subjects showed no increased inhibitory effect (12.5 plus or 
minus 7.9 and 12.5 plus or minus 6.6). These findings demonstrate 
that the sodium reabsorption inhibitory effect is produced by the secretions 
from some but not all salivary glands of patients with CF. 
