Characteristics of Proline-rich Salivary Proteins Induced in Rat Parotid Glands by Tannins in Bean Hull

Feeding rats a diet containing bean-hull causes hypertropy in their parotid glands due to the high tannin content. The amount of feedintake of rats led bean-hull was higher than that of rats fed a standard diet. However, the increase in body weight of rats fed bean-hull was lower than that of rats fed a standard diet, which resulted in significantly low feed efficiency of the bean-hull containing diet. Within one week, parotid glands significantly enlarged and a series of proline-rich proteins (PRPs) were produced, which were similar to those induced by feeding high-tannin sorghum with flight differences in molecular weights. Even though the direct comparison between PRPs produced by the bean-hull containing diet and those induced by the high sorghum diet is not appropriate due to laboratory inconsistences, several new PRPs were produced by high tannin diets in both experiments. Differences in molecular weights of PRPs induced in two different tannin sources must be funker investigated to be fully characterized. These morphological and biochemical changes have now been demonstrated to occur in response to the ingestion of tannins, presumably to diminish the anti-nutritional effects of tannins.