A comparative quantitative histological investigation of atrophic changes in the major salivary glands of liquid-fed rats.

Adult male rats were maintained on a wholly liquid diet for 9 days. The three pairs of major glands were removed, weighed, histologically sectioned and examined by stereological and morphometric techniques. The results were compared with the same glands from control rats maintained on normal hard diet and water, and the extent of the differences was compared between the three different types of gland. Up to 50% of the serous acinar volume in the parotid glands, but only 15% in the submandibular glands, was lost after liquid feeding. There was no loss of the mucous acinar tissue in the sublingual gland. Mean acinar diameters were reduced by 33% in parotids and 15% in submandibular glands after liquid feeding, whereas the mucous acini of the sublingual gland remained unaltered. The results point to varying levels of susceptibility to the loss of masticatory reflexes between the parotid serous acini and the submandibular serous acini, and show that the morphology of the sublingual mucous acini is independent of masticatory reflex stimulation. The reductions in acinar diameters suggest that most of the glandular atrophy after liquid feeding is due to acinar cell shrinkage rather than to losses of acinar cell numbers in both parotid and submandibular glands.