Abstract
We previously demonstrated that irritating dietary substances such as papain and capsaicin induced cystatin S in submandibular saliva of rats. In order to expand knowledge about induction of salivary proteins by a dietary constituent, we investigated the effects of dietary quinine, the bitter principle of tonic water, on the submandibular gland and its saliva in rats. Dietary quinine (973–9730 ppm) increased the weight of the submandibular gland and induced at least six cystatins (apparent molecular weight: 14–45 kDa) and induced/upregulated at least five quinine-binding proteins (apparent molecular weight: 14–105 kDa) in submandibular saliva by three days after the beginning of feeding. In contrast, the group treated repeatedly with 97.3 ppm–saturated quinine solutions through an oral cannula showed a similar electrophoretic pattern of saliva as for the intact control group (no cystatin and very low quinine-binding protein). These results suggest that the combination of masticatory and gustatory stimulation is required for induction of cystatins and upregulation of quinine-binding proteins in saliva by dietary quinine. [J Physiol Sci. 2008;58 Suppl:S141]
