Systemic and local effects of long-term exposure to alkaline drinking water in rats

Alkaline conditions in the oral cavity may be caused by a variety of stimul i, including tobacco products, antacids, alkaline drinking water or bicarbo nate toothpaste. The effects of alkaline pH on oral mucosa have not been sy stematically studied. To assess the systemic (organ) and local (oral mucosa l) effects of alkalinity, drinking water supplemented with Ca(OH)(2) or NaO H, with pH 11.2 or 12 was administered to rats (n = 36) for 52 weeks. Tissu es were subjected to histopathological examination; oral mucosal biopsy sam ples were also subjected to immunohistochemical (IHC) analyses for pankerat in, CK19, CK5, CK4, PCNA, ICAM-1, CD44, CD68, S-100, HSP 60, HSP70, and HSP 90. At completion of the study, animals in the study groups had lower body weig hts (up to 29% less) than controls despite equal food and water intake, sug gesting a systemic response to the alkaline treatment. The lowest body weig ht was found in rats exposed to water with the highest pH value and startin g the experiment when young (6 weeks). No histological changes attributable to alkaline exposure occurred in the oral mucosa or other tissues studied. Alkaline exposure did not affect cell proliferation in the oral epithelium , as shown by the equal expression of PCNA in groups. The up-regulation of HSP70 protein expression in the oral mucosa of rats exposed to alkaline wat er, especially Ca(OH)(2) treated rats, may indicate a protective response. Intercellular adhesion molecule-1 (ICAM-1) positivity was lost in 6/12 rats treated with Ca(OH)(2) with pH 11.2, and loss of CD44 expression was seen in 3/6 rats in both study groups exposed to alkaline water with pH 12. The results suggest that the oral mucosa in rats is resistant to the effects of highly alkaline drinking water. However, high alkalinity may have some unk nown systemic effects leading to growth retardation, the cause of which rem ains to be determined.