The effects of tannin-rich diet on protein composition of parotid and submandibular glands of Guinea Pig

  Tannins are plant-derived polyphenolic compounds that are widely found in foods, particularly in fruits and beverages. These materials are water-soluble and able to precipitate proteins from aqueous solutions. It had been shown that feeding some animals such as rat and mouse with tannins mimicks the effects of isoproterenol on salivary glands. Tannins stimulate β-receptors by some indirect mechanisms. In the present study, two groups of male Guinea pigs (Cavia porecellus) were selected. The first group was fed with diets high in tannins for 20 days and the second group was chosen as control. After using tannins, both parotid and submandibular glands revealed a significant increase in weight. Biochemical studies indicated that tannins decreased the amount of total protein and amylase in parotid gland, but on the other hand in submandibular gland, total protein and amylase increased. Sodium dodecylsulfate polyacrylamide gel electrophoresis from parotid gland showed three protein bands with molecular weights of 67, 52 and 14 Kds that were weakly stained as compared to control ones. Extracted protein from tannin-treated submandibular gland showed protein bands with molecular weights of about 67, 52 and 16.5 Kds respectively. These bands were stronger than control group. It seems that protein bands with molecular weights of about 67, 16.5 and 14 Kds belong to a group of proline-rich proteins. Protein band with molecular weight of about 52 Kd probably belongs to amylase. These differences probably indicate that the number of β1- and β2-adrenergic receptors may be varied in both parotid and submandibular secretory cells. On the other hand, it seems that β1-receptors are mainly present in parotid gland, but in submandibular gland, β2-receptors are predominant.