[The effect of the distribution of polar groups in a steroid molecule on its inhibition of Na+,K+-ATPase].

Transformed steroids having oxidized side chains in the D ring site and varying by polarity of the substituent at the ring A C(3)-position--acetates, glucosides or with free hydroxyls--in the concentration range 1 X 10(-4) - 1 X 10(-7) M were found to inhibit Na+, K+-ATPase. The extent of inhibition decreases with the rise in the polarity of the A region of the steroid molecule. With the compound devoid of polar groups in the D region an increase in the inhibitory activity is observed on passing from 3-acetate to 3-glucoside. The data obtained confirm the relationship between the extent of Na+, K+-ATPase inhibition and biphilicity of the molecule.