RESUMO
<b>Background</b>: Spring water exhibits “aging”, characterized by increased oxidation reduction potential (ORP) and diminished therapeutic efficacy. However, the influence of spring water ORP on the body during bathing is unknown. Gout has been treated by spa bathing and by acupuncture, as well as pharmacologically. We accordingly examined the relationship between ORP and uric acid excretion, and that between ORP and ryodoraku current, which is closely related to acupuncture.<br><b>Design</b>: Three groups of three volunteers each bathed in a different solution; sulphur-containing spring water, bicarbonate-containing spring water, or tap water. Serial changes in uric acid excretion and ryodoraku were measured.<br><b>Results</b>: Urinary uric acid: creatinine ratio and ryodoraku current increased after sulphur spring water bathing and diminished after tap water bathing. Urinary ORP was negatively correlated with urinary uric acid: creatinine ratio and urinary pH. Ryodoraku current and urine ORP changed in opposite directions.<br><b>Conclusion</b>: Bathing water ORP affected urinary ORP, urinary uric acid excretion, and ryodoraku current. Urinary ORP was assumed to reflect interstitial fluid ORP, suggesting that uric acid excretion and ryodoraku current were affected by interstitial fluid ORP. These findings appeared to indicate that ORP influenced cell membrane potential because voltage-dependent transporters or channels exist in the kidney and epidermis. Moreover, as urinary ORP was negatively correlated with urinary pH, ORP seemed to electrically buffer pH. As these findings can be explained by the Nernst equation by which ORP is derived, ORP of spring water might electrically influence the organism during bathing.