We describe the effects of Sairei-to, a Chinese herbal medicine, on aminonucleoside-induced nephrotic rats (ANNR), and analyze the urinary excretion of protein and phosphatidylinositol (PI) turnover via prostaglandin E2 (PGE2) receptors in isolated glomeruli. Sairei-to suppressed urinary excretion of protein and PGE2 in ANNR, and inhibited acceleration of PI turnover in isolated nephrotic glomeruli. The affected responsiveness of the PI turnover system to PGE2 in a nephrotic state was presumed to be normalized by Sairei-to. These findings suggest that Sairei-to restores abnormal changes in the PI turnover system in ANNR kidneys, and thereby inhibit excretion of protein into the urine.