Potassium and magnesium retaining potency and efficacy of triamterene and analogues in conscious saline-loaded rats.

The effect of triamterene and analogues on the acute renal excretion of K+ and Mg2+ was investigated in conscious saline-loaded rats. The maximum retention (Emax) value of the potassium and magnesium retaining efficacy is almost independent of the structure of the compound and depends only on the initial basal value of ion excretion (E0). Triamterene and analogues display a comparable magnesium retaining efficacy. This can be explained by activity against the same renal Mg2+ transportation system. There was a relation between the ED50 values for the potassium and magnesium retaining properties of triamterene derivatives. Both the potassium and the magnesium retaining potency are dependent on the basicity as well as on the lipophilicity of the side chain of the triamterene derivatives. The part of the molecule responsible for the antimagnesiuretic properties of the derivatives seems to be sensitive to steric influences.