The chronically ligated submandibular salivary duct of the rabbit as a possible model for cystic fibrosis [proceedings].

Schulz (1969) showed that the raised Na concentration in the sweat of 
children suffering from cystic fibrosis was due to a defect in 
Na reabsorption in the duct epithelium, but somewhat surprisingly the transepithelial 
potential difference (p.d.) is the same as that in normal controls. 
Na transport is also reduced in the chronically ligated salivary duct 
of the rabbit submandibular gland (Fraser & Smaje, 1978), and because 
p.d. is unaffected, the ligated gland may be a useful model 
of this aspect of cystic fibrosis. Here we would like to 
report a further similarity to cystic fibrosis; duct ligation leads to 
goblet cell hyperplasia which also occurs in the salivary glands in 
cystic fibrosis (Lev & Spicer, 1965). Sections of the salivary duct 
6 microm thick were taken at 60 microm intervals from ducts 
which had been ligated for between 1 and 5 weeks and 
from their contralateral controls following fixation by immersion. Ligation resulted in 
an increase in luminal diameter by distension of the previously convoluted 
epithelium, but there was no significant change in epithelial surface area. 
The number of cell layers appeared to have increased however and 
there was a proliferation of goblet cells. The mucus in these 
cells was stained by alcian blue at pH 1 indicating the 
presence of sulphomucin. The mean goblet cell density rose from 7.62 
plus or minus 4.73 mm-2 (mean plus or minus S.E. of 
the mean, n = 6) in controls to 114 plus or 
minus 49.6 in ligated ducts. The transepithelial Na flux in the 
same ducts was reduced from 10.1 plus or minus 0.79 n-mole 
cm-2 sec-1 to 1.6 plus or minus 0.84 while p.d. remained 
at -22 mV, similar to those results previously reported. There was 
no significant correlation between the degree of diminution of Na transport 
and the density of goblet cells but there was a positive 
correlation (r = 0.90) between the number of goblet cells in 
the control and contralateral ligated ducts. 