THE EFFECTS OF STREPTOZOTOCIN DIABETES ON SALIVARY-MEDIATED BACTERIALAGGREGATION AND ADHERENCE

Diabetic rats are known to have an increased susceptibility to dental caries and major alterations in parotid salivary composition. Salivary proteins play an important part in oral health maintenance; thus spec ific changes in salivary protein composition in diabetic animals might alter the ecological balance in favour of cariogenic bacteria, and to ward the initiation and progression of the disease process. The abilit y of whole, pare tid and submandibular salivas from control and strept ozotocin-diabetic rats to mediate the aggregation and adherence to hyd roxyapatite of mutans streptococci was examined. Salivary-mediated bac terial aggregating activity was significantly reduced in whole and par otid salivas from diabetic rats, but bacterial adherence to hydroxyapa tite was unaffected. The aggregating and adherence activities of rat w hole saliva were derived mainly from parotid saliva, which contains pr edominantly low molecular-weight proteins and glycoproteins (< 200 kDa ), but rat parotid saliva was capable of interacting with the bacteria l receptor for the high molecular-weight aggregating factor in human s aliva. SDS-PAGE of parotid saliva revealed that a number of proteins, including the basic and acid proline-rich proteins, were altered in th e salivas of diabetic animals. After incubation with either Streptococ cus mutans or hydroxyapatite several protein bands were depleted, and thus a variety of proteins and glycoproteins may be responsible for th e adherence and aggregating activity of rat parotid saliva.