Production of salivary microlithiasis in cats by parasympathectomy: light and electron microscopy

Salivary glands of cat were examined from 1 to 42 days following parasympathectomy and compared with contralateral normal control glands. Microliths were detected by light microscopy in none of 11 parotid, 31 out of 41 submandibular and four out of 22 sublingual glands following parasympathectomy, and one out of 19 parotid, five out of 28 submandibular and four out of 15 sublingual normal control glands. The greatly increased occurrence of microliths in the submandibular gland was statistically significant. Microliths in the parasympathectomized submandibular glands were detected by light microscopy most often in ductal lumina, followed by acinar lumina, ductal parenchyma, interstitial stroma, and acinar parenchyma. They were detected by electron microscopy also in the basement membrane overlying protruding processes of myoepithelial cells and in intraparenchymal macrophages. Intracellular microliths were in phagosomes. In the parasympathectomized submandibular glands, parenchymal atrophy was seen and particularly involved the striated ducts; secretory material and cellular debris were seen in lumina; and macrophages and neutrophils were more apparent than normally. The great increase of microlithiasis in the submandibular gland appears to be the result of secretory inactivity, and microliths appear to form in stagnant secretory material and cellular debris in lumina and in phagosomes of parenchymal cells.