The role of urinary prostaglandin E and cyclic AMP in the polyuria of hypokalemia in rats.

The effect of potassium depletion on urinary prostaglandin E and cyclic AMP excretion was studied in female Sprague-Dawley and in Brattleboro rats. The animals were fed a potassium-free diet for 20 days which resulted in an average decrease in serum potassium of 25% in both strains. In the Sprague-Dawley rats, potassium depletion increased urine volume from 5.5 +/- 0.9 ml/day to 25.9 +/- 3.5 ml/day (p less than 0.001), decreased urinary osmolality from 1483 +/- 87 mosmol/kg H2O to 372 +/- 12 mosmol/kg H2O (p less than 0.001) and suppressed urinary cyclic AMP excretion from 56.95 +/- 3.81 nmoles/day to 0.83 +/- 0.40 nmoles/day (p less than 0.001). Potassium depletion in the Brattleboro rats did not affect these parameters. Excretion of prostaglandin E-like immunoreactivity in urine did not change in either strain with potassium depletion. The findings support the hypothesis that prostaglandins do not play a significant role in the polyuria caused by potassium deficiency in rats. Hypokalemia may cause polyuria by suppression of vasopressin-sensitive cyclic AMP generation, leading to a decrease in water permeability.