Abstract

In the folk-medicine, several kinds of crude drugs are used as diuretics. Twenty three kinds of diuretic drugs were chosen, and examined for their effects on the horse kidney (Na+ + K+)-adenosine triphosphatase (ATPase), which is an intrinsic enzyme of the plasma membrane and responsible for the active transport of Na+ and K+ across the membrane. Twenty one out of twenty three kinds of ethanol extracts of diuretic drugs inhibited the kidney (Na+ + K+)-ATPase activity. The intensity of the inhibition of these drugs was compared by estimating the amounts of their ethanol extracts which inhibited the (Na+ + K+)-ATPase activity by 50% (I50, micrograms/ml). Among these drugs, Atractylodis Lanceae Rhizoma (I50 = 12.8) Atractylodis Rhizoma (I50 = 15.2), Plantaginis Semen (I50 = 16.0), Plantaginis Herba (I50 = 16.0) and Alismatis Rhizoma (I50 = 22.0), have strong inhibitory effects on the kidney (Na+ + K+)-ATPase activity. The ethanol extracts of the rhizomes of Atractylodes lancea De Candolle and Atractylodis japonica Kitamura were examined with varying concentrations of ATP and ouabain. The mode of inhibition of these two extracts on the (Na+ + K+)-ATPase activity appeared to be uncompetitive with respect to ATP as judged from Lineweaver-Burk plot. The ethanol extract of Atractylodes japonica Kitamura decreased the I50 for ouabain from 1.6 x 10(-7) to 7.0 x 10(-9) M, while that of Atractylodes lancea De Candolle did not change the I50 for ouabain.