A Comparison of Certain Properties from Specific Major Salivary Glands of Caries-resistant and Caries-susceptible Rats

¹ Departments of Microbiology and Public Health, Zoology, and Chemistry, Michigan State University East Lansing, Michigan

Whole, parotid, and submaxillary-sublingual salivas from caries-resistant and caries-susceptible rats were analyzed for amylase activity, relative viscosity, rate of flow, pH, and buffering capacity.

More than 99 per cent of the amylase activity of saliva originated in the parotid glands of these animals. Parotid and whole salivas from susceptible rats showed greater amylase activity than these salivas from resistant rats.

When the various salivas were collected at room temperature, whole and submaxillary-sublingual salivas from resistant rats were more viscous than these salivas from susceptible rats. When whole saliva was collected in tubes submerged in ice, the difference between resistants and susceptibles was no longer observed. There was no difference in the relative viscosity in the parotid secretions between the two lines of rats. Comparison of salivas within the lines of rats showed that parotid saliva was less viscous than submaxillary-sublingual saliva, whereas whole saliva gave intermediate values.

The mean rate of flow and pH of the parotid, submaxillary-sublingual, and whole secretions were not essentially different in resistant and susceptible rats. Within each line of rats, however, the rate of flow of each saliva differed. Whole saliva from unoperated rats showed the greatest flow rate—parotid saliva was slowest and submaxillary-sublingual saliva was intermediate.

Buffering capacity, determined by titratable alkalinity, was significantly greater in susceptible than in resistant whole and submaxillary-sublingual salivas.