Sialochemical profile of X-irradiated major salivary glands in the rat.

The purpose of this study was to examine various sialochemical parameters in parotid (P) and submandibular (SM) secreted saliva of irradiated rats. Various doses of radiation from 2.5 to 15 Gy were administered to the head and neck region and the saliva was evaluated for its amylase activity and the concentration of sodium (Na), potassium (K) and total protein. Saliva samples containing equal amounts of proteins were also electrophoresed on separatory SDS gels, silver-stained and examined for possible qualitative alterations. The total protein concentrations of P saliva showed a radiation dose-dependent reduction at 3 days and 3 and 9 months following 15 Gy of 93%, 82% and 73% (p < 0.01), respectively. Forty days after the 15 Gy irradiation the reduction was not as severe (55%, NS). Three and 40 days post 15 Gy, amylase activity demonstrated a similar pattern of reduction, 98% and 89% (p < 0.01), respectively. In contrast to the P, no quantitative changes in the protein concentrations of the SM saliva were detected. As for the qualitative profiles of separated proteins, no radiation-induced changes were found for either P or SM at 3 and 40 days or 3 and 9 months, as compared with controls. The electrolyte concentrations were found to be flow-rate dependent. The Na concentrations of P saliva at 3 and 40 days following 15 Gy were reduced by 65% and 83% (p < 0.01), respectively. For SM saliva, the Na concentrations were reduced at 40 days by 58% (p < 0.05). The K concentration of P saliva increased at 40 days by 79% (p < 0.05). The data suggest that the various observed sialochemical changes could result from a reduction in the salivary flow rate and/or the number of surviving, normally functioning parenchymal cells. Thus, it is suggested that no salivary compositional alterations were directly induced by radiation but were secondary effects.