Acid and alkaline ribonucleases of human parotid, submaxillary, and whole saliva

Abstract

Parotid and submaxillary saliva samples were collected from a number of adults and children with the use of specially constructed and carefully fitted appliances. These samples and whole salivas were examined for the presence of several ribonucleases and ribonuclease inhibitor. Both acid and alkaline ribonucleases were demonstrated in the parotid and submaxillary secretions and in whole saliva of men, women, and children. Some properties of the ribonucleases of the parotid and submaxillary secretions were studied, and conditions for the assay of the two enzymes were determined. Analysis of parotid, submaxillary, and whole salivas collected sequentially from the same subject has led to the conclusion that the ribonuclease activity of the glandular secretions accounts for a large percentage of the total RNase activity found in whole saliva at pH's 6.5 and 7.8 and that the salivary RNases may play an auxiliary role to pancreatic RNase in gastrointestinal digestion. Since only the alkaline enzyme is found in human serum, it is unlikely that serum is the source of salivary RNase activity. Ribonuclease levels have been determined in groups of normal adults and children. Neither RNase inhibitor nor latent RNase activity has been found in parotid or submaxillary saliva.