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The effect of aging on the rat submandibular gland was studied by using ulIrastructural, ultrastructural cytochemical and biochemical techniques. There was an age-related clumping of the nucleolar-associated and peripheral chromatin in many of the acinar cells and a decrease in the number of cisternae of rough endoplasmic reticulum. Many aged acinar cells were binucleated. There was also an agc-related increase in pigment granules throughout the gland. These membrane bound granules consisted of a lipid droplet and an associated dense cap which had a granular matrix and pigment droplets. The lead capture method for acid phosphatase activity demonstrated that activity was associated with the granular matrix of the dense cap. These results were corrclated with the age-related increase in acid phosphatase activity as determined by colorimetric procedures.There was an age-related increase in thc number of cells characterized by small secretory gr,anules. These cells were found as part of the intercalated ducts or at the junction of the duct with the acini. Oncocytes were also found as par1 of the parenchyma of the aged submandibular gland. Thcse cells were charactcrized by the pleomorphic mitochondria that fill their cytoplasm. Occasionally, cells that possessed extraordinary numbers of mitochondria and small secretory granules were also observed.The determinations of total DNA and R N A revealed an age-related deaease in RNA while there was no significant change in the concentration of DNA.Several age-related changes have been reported to occur in the submandibular gland. One of these changes was the observation of "oncocytes" in the submandibular gland of man. Hamper1 ('3 1, '33) described these altered cpithelial cells as having an eosinophilic granular cytoplasm.Oncocytes (Andrew, '49) have also been reported in the submandibular gland of senile rats. However, these cells were described as aci nar cells that possessed a foamy reticulated cytoplasm, reduced cytoplasmic basophilia and either pycnotic or hypertrophic nuclei, with thc latter having a pronounced nucleolus. More recently, several studies of oncocytic tumors in man have described the ultrastructural morphology of the granular eosinophilic cells that were previously reported by Hamperl. The cytoplasm of these cells was packed with pleomorphic mitochondria (Tandler and Shipkey, '64; Balogh and Roth, '65; McGavran, '65).There appears to be some discrepancy in the reported description of oncocytes as they appear in the rat and human submandibular gland. This discrepancy led the author to examine the age-related changes that occur in thc ultrastructural morphology of the rat sub-J. MOKPH.. 130: 337-352. mandibular gland. It is also the purpose of this investigation to correlate these age-related alterations in morphology with age-related changes that occur in the cytochemistry and biochemistry of the rat submandibular gland. MATERIA1,S AND METHODSMale and female Wistar rats, 4 months, 9 months and 24 months of age were housed in wire mesh cages and ...

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Tear glycoproteins are derived from four principal sources. In R fluid, an inducible lacrimal secretion predominates. In C fluid, a constitutive sIgA secretion predominates, augmented by a serum exudate and SGs derived at least in part from the epithelium. In R fluid and pellet extracts, the SGs consist primarily of a 450-500 kDa species that is most probably derived from the plasma membrane. Larger antigenically related SGs are prevalent in C fluid.