Production of proline-rich proteins by the parotid glands of rats is enhanced by feeding diets containing tannins from faba beans (Vicia faba L.).
Feeding a casein-based diet with either 400 g/kg of tannin-containing faba bean hulls (Vicia faba L.) (1.41% condensed tannins) or 60 g/kg of a tannin-rich hull extract of faba beans (1.99% condensed tannins) to rats over a period of 7 d resulted in a 2.6 and 1.5 fold increase in weight of the parotid glands, respectively, (P < 0.05) and a corresponding 5.5 and 3.7 fold increase in the level of proline-rich proteins in the glands (P < 0.05). In a dose-response experiment, increasing the level of tannin-rich hull extract in the diet (0.0, 3.8, 7.5, 15.0, 30.0 and 60.0 g/kg) resulted in a linear increase in both the relative size of parotid glands (R2 = 0.90; P < 0.05) and the quantity of proline-rich proteins in the glands (R2 = 0.89; P < 0.05). The apparent digestibility of total (R2 = 0.97) and individual amino acids (R2 varied from 0.27 to 0.99) decreased linearly (P < 0.05). The quantity of proline-rich proteins in the cecum of rats was estimated from the decrease in digestibility of proline, glycine and glutamic acid. The estimated secretions of proline-rich proteins, when calculated on the basis of the three respective amino acids, were 3.5, 3.5 and 3.9 mg of proline-rich proteins per 10 mg of additional hull extract (21.8% condensed tannins). The results indicate that tannins from faba beans stimulate the parotid glands to increase the secretion of proline-rich proteins in rats. The proline-rich proteins then interact with dietary condensed tannins to reduce their antinutritional effects.
Jansman
A J
AJ
TNO Nutrition and Food Research, Department of Animal Nutriton and Physiology, Wageningen, The Netherlands.
Frohlich
A A
AA
Marquardt
R R
RR
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002482:Cellulose / Q000008:administration & dosage; D004032:Diet; D004063:Digestion; D004435:Eating; D007887:Fabaceae; D008297:Male; D009929:Organ Size; D010306:Parotid Gland / Q000254:growth & development / Q000378:metabolism*; D010946:Plants, Medicinal; D011392:Proline; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D012471:Salivary Proteins and Peptides / Q000096:biosynthesis* / Q000737:chemistry; D013634:Tannins / Q000008:administration & dosage*; D015430:Weight Gain
D000596:Amino Acids; D012471:Salivary Proteins and Peptides; D013634:Tannins; D002482:Cellulose; D011392:Proline