Increased concentrations of a circulating sodium pump inhibitor in essential hypertension and uraemia and its partial purification from haemofiltrate.

Patients with essential hypertension have 3.2 fold and patients with chronic uraemia 11.7 fold higher serum concentrations of endogenous digitalis-like activity than normotensives (76.3 +/- 9.3 nM). Upon haemodialysis this serum activity drops to almost normal values. A low molecular factor could be partially purified from 4000 l haemofiltrate.