Effect of High Isoflavone Content Diet on the Salivary Glands

Objective: Soya is increasingly used as a food additive. In women it is recommended as an alternative to hormonal replacement therapy and a preventive agent against breast cancer, osteoporosis. Genistein and daidzein are the most abundant isoflavones present in soy and even modest amounts may exert biological effects in vivo. The aim of this study was to evaluate the effect of soya-diet and the refeeding on the rat salivary glands. Previously we have shown soya hypertrophy and hyperplasia. Hyperplasia for intercalated ducts was more dominating. Methods: Animals were fed with either standard rat chow (group C; n=16) or soya bean (group S; n=20) for five days. On the sixth day the parotids as well as the submandibular and sublingual glands were excised. Wet weight, DNA and protein contents were determined in each organ. Levels of significance were calculated by the Student's t-test. Results: In rats fed with soya, parotid weight was 56 percent higher than the control values (C: 287±64mg, S: 512±156mg; p<0,001). The weight of parotid is continued to increase for further two days after subsequent refeeding with normal diet, declining to the control level only on the fifth day. Parotid DNA content per unit organ weight did not alter, while total organ DNA contents proportionally increased with increase of wet tissue weight in soya treated rats. Soya feeding did not change either submandibular or sublingual gland wet weight. Conclusion: Dietary isoflavones in soya may differentially influence salivary growth by modulating signal transduction of the receptor tyrosine kinase. The adverse effects on the parotid and submandibular glands remain to be studied. Supported by: ETT 247/2003-5, OTKA T-046511, Hungary