The Journal of clinical investigation
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In order to study the mechanism of enhanced potassium excretion by the remaining nephrons of the remnant kidney, micropuncture and clearance experiments were carried out in rats after surgical ablation of 3/4 of the total renal mass. The potassium intake in all animals was approximately 5 meq/day. Animals were studied 24 h and 10-14 days after 3/4 nephrectomy. ⋯ In these animals, no addition of K(+) occurred beyond the distal tubules. Normal rats infused with 0.15 M KCl to acutely elevate serum K(+) concentration, demonstrated reabsorption of K(+) in the distal tubule and a large addition of K(+) to the urine beyond the distal tubule. We conclude that the collecting duct is the major site of regulation of urinary potassium excretion in normal rats and is responsible for the adaptation to nephron loss by the remnant kidney.