Morphologic effects of hypervitaminosis A on rat submandibular gland.

Young male Sprague-Dawley rats were fed oral supplements of vitamin A; either a subtoxic dose of 5000 i.u./day for 16 weeks (10 animals), or a toxic dose of 15,OOOi.u./day for 16 days (5 animals). High-dose animals exhibited signs of acute toxicity; low-dose animals demonstrated only less weight gain than controls. Vitamin A sera and liver levels evidenced intoxication. Light and electron microscopy were conducted upon acini, intercalated ducts, and striated-granular ducts of the submandibular gland. Acinar cells evidenced rough endoplasmic reticulum clefting and hyperplasia of both rough endoplasmic reticulum and Golgi apparatus similar to changes produced by pilocarpine or isoproterenol and interpreted as hyperactivity. Also increased were the number of degenerating acinar cells. Striated-granular duct cells were similar to controls except for increased cellular degeneration. Intercalated ducts appeared unaffected. Abnormalities were more pronounced in short-term, toxic hypervitaminosis A than long-term, subtoxic hypervitaminosis A.