Protein intake conditions the diuresis seen after relief of bilateral ureteral obstruction in the rat.

Natriuresis and diuresis occur in experimental animals after release of bilateral ureteral obstruction. Accumulation of urea and/or other natriuretic factors during the interval of complete obstruction may play a role in the ensuing postobstructive diuresis. The present experiments examine the potential role of dietary protein intake in conditioning the magnitude of the postobstructive diuresis after unilateral release of bilateral ureteral obstruction of 24-hr duration in the rat. Rats were fed isocaloric diets containing high (40% casein) or low (6% casein) protein for 4 weeks prior to obstruction. Rats fed a high protein diet had greater urine flows and fractional excretion of sodium and potassium after relief of obstruction than rats fed a low protein diet. Increased excretion of urea accounted for only part of the greater diuresis seen in rats fed a high protein diet. Hence, greater accumulation of other natriuretic factors during the period of obstruction in rats fed a high protein diet must play a role in the increased diuresis seen in this group of animals after release of obstruction.