Induction of salivary polypeptides associated with parotid hypertrophy by gallotannins administered topically into the mouse mouth

Abstract

Isoproterenol-induced salivary polypeptides (IISP), a group of proline-rich proteins synthesized by mouseparotids, have been considered as markers for isoproterenol-induced parotid hypertrophy. Rodents fed diets containinghigh-tannin cereals (sorghum), also develop parotid hypertrophy. To test whether tannins are directly involved inprovoking sialotrophic growth, we studied the effect of intraperitoneal and topical oral administrations of tannic acid (TA)on the induction of IISP polypeptides in endogamic mice (A/Snell). TA was characterized by HPLC chromatography andspectral analysis and shown to be composed solely of gallotannins, a complex family of glucose and gallic acid esters. IISPpolypeptides were monitored in saliva by SDS–polyacrylamide gel electrophoresis during 36 h after ending TAstimulation. Single daily intraperitoneal administrations of TA for 3 consecutive days (0.033 mg/g bw/day), at variance ofparallel administrations of isoproterenol (0.042 mg/g bw/day) failed to induce IISP polypeptides. However, repeatedtopical applications of TA into the mouse mouths (1.21 mg/g bw divided into three equal doses given at 4-h intervals withina single day) resulted in unequivocal induction of IISP polypeptides. That response was clearly intensified by increasing thestimulation frequency to eight equivalent doses given at 1.5-h intervals within a single day (corresponding to 3.23 mg/gbw) and even further by repeating this protocol for 3 days. Under these productive schemes of stimulations by TA,electrophoretic fractionation of parotid homogenates showed new polypeptide bands migrating in parallel to salivary IISP.These results suggest that topically administered gallotannins are effective inducers of trophic growth in mouse parotids.