Effect of chronic hypokalaemia on renal concentrating ability and secretion of arginine vasopressin.

Two patients with a Bartter-like syndrome, who had been hypokalaemic for 129 and 55 months, and 13 normokalaemic control subjects were investigated during 24 h of water deprivation. The hypokalaemic patients had urine volumes, urine osmolalities, osmolar clearances and tubular capacities for water reabsorption within the normal range. During thirst, plasma-arginine vasopressin increased much more markedly in the patients (3.4 to 11.1 pmol/l and 3.0 to 17.7 pmol/l) than in the control subjects (2.1 pmol/l (median), range 1.0-3.1, to 3.7 pmol/l, range 1.7-6.4). Plasma angiotensin II increased during water deprivation in the patients (33 to 53 pmol/l and 147 to 208 pmol/l) but not in the control subjects (9 pmol/l (median), range 3-15, to 11 pmol/l, range 3-15). Plasma aldosterone was the same in patients and control subjects and did not change in response to thirst. It is suggested that renal concentrating ability can be preserved in patients with chronic potassium depletion by means of a compensatory increase in the secretion of antidiuretic hormone.