Effect of Kampo Herbal Medicines on Murine Water Metabolism in a Microgravity Environment

To determine the possibility of new applications of Oriental medicines, we examined the changes in water metabolism of mice that underwent microgravity and were treated with Kampo medicines. Male ICR mice were used in this experiment. Eight extracts of Kampo herbal medicines were dissolved in water and added to the drinking water administered to mice at 1 g/kg body weight for two days. The microgravity experiment was performed at the Japan Microgravity Center. We used a drop-shaft type microgravity experimental system with a free fall of 490 m. Before the drop, 7 ml of physiological saline was injected intraperitoneally. Under fasting and dehydration, body weights were measured and loss of body weight was calculated as urine. Blood samples were collected 24 hours after the microgravity experiment, and the antidiuretic hormone (ADH) in plasma related to water metabolism was measured by the radioimmunoassay (RIA) method. Heat shock protein in the spleen was measured by the enzyme-linked immunosolvent assay (ELISA) method. In the Hachimi-jio-gan and Hochu-ekki-to groups in microgravity, a decrease of urine was observed, which significantly suppressed the increase of ADH due to microgravity. Hachimi-jio-gan reduced the content of heat shock protein (HSP) 70 in the spleen. It is suggested that Hachimi-jio-gan and Hochu-ekki-to could be used as water metabolism adjustment reagents in a space environment. Furthermore, it is suggested that Hachimi-jio-gan could ease the stresses caused by microgravity. The physiological changes resulting from a microgravity environment are serious problems for space flight. Pre-treatment with Kampo medicines is expected to prevent, ease and treat these problems.