Objective: To Explore pathological mechanisms of syndrome of retention of dampness in middle energizer and mechanisms of Pingwei Powder for treatment of the syndrome of retention of dampness in middle energizer. Methods: In the model rat of retention of dampness in middle energizer treated by Pingwei Powder combined with diuretics

contents of plasma antidiuretic hormone （ADH） and Na+ K+ in red blood cells were investigated. Results: Contents of plasma ADH and Na+ of red blood cells increased and K+ decreased significantly in model group as compared with those in normal group （P<0.01 WT5"BZ] or P< 0.05）. After treatment of Pingwei Powder. ADH content was restored basically normal

intracellular Na+ content decreased to nearly normal and K+ did not significantly change in high dose

middle dose and low dose group and the group combined with Zexie （Rhizoma Alismatis）. and ADH increased and K+ Na+ decreased significantly in medicine-administrated normal rats as compared with normal group （P<0.05 or P<0. 01）. Conclusion: The increase of plasma ADH and intracellular Na+ and the decrease of K+ play an important role in formation of retention of dampness in middle energizer. The mechanism of Pingwei Powder for treatment of retention of dampness in middle energizer is related with the regulation of plasma ADH and intracellular Na+ and K+ contents

possibly with bidirectional regulation.