Zinc deficiency-induced changes in rat parotid salivary proteins

This study was undertaken to determine the effects of zinc deficiency on rat parotid salivary proteins. Male rats were fed a pelleted diet containing either 40 ppm Zn (ad libitum- and pair-fed control groups) or 0.9 ppm Zn (zinc-deficient group) for a period of 4 weeks. At the time they were killed, stimulated parotid saliva was collected and analyzed for concentration and composition of secretory protein. In addition, gland specimens were examined ultrastructurally, and liver and serum samples were assayed for zinc concentration. The zinc-deficient group exhibited retarded body growth, decreased appetite and significantly lower serum and liver zinc concentrations. The most significant finding in the saliva of the deficient animals was the marked reduction in acidic proline-rich proteins. Parotid gland secretory activity also seemed reduced. Morphologically, distinctive secretory granules were observed in the acini of the deficient animals. The altered composition of salivary secretory proteins coupled with a diminished flow rate may, in part, be responsible for the increased susceptibility to dental caries in zinc-deficient rats.