Effect of potassium depletion on renal tubular function in the rat.
1. In order to investigate the effects of K+ depletion on renal function, micropuncture studies were performed on anaesthetized rats which had been kept on a K+-deficient diet for 2 weeks; results were compared with those from control animals. 2. In the K+-depleted animals, values for total glomerular filtration rate and single-nephron filtration rate were significantly lower than in controls. Urine osmolality was also reduced; this was associated with reductions in the osmolality, Na+ concentration and K+ concentration of papillary interstitial fluid. No significant difference between urine and papillary osmolality was observed. 3. Fractional reabsorption by the proximal convoluted tubule was enhanced in the K+-depleted animals; end-proximal fluid delivery was markedly reduced. 4. Absolute, but not fractional, delivery of K+ to the beginning of the distal tubule was reduced in the K+-depleted animals. In contrast to observations in control rats, no net secretion of K+ into the distal tubule occurred and there was indirect evidence of K+ reabsorption in the collecting duct. 5. K+ depletion was associated with reductions in the delivery of Na+ and water to early and late regions of the distal tubule, whereas excretion rates of Na+ and water were unaffected. 6. It is suggested that the reduction in Na+ delivery to the loop of Henle (arising from the changes in filtration rate and proximal tubular reabsorption) might contribute to the reduced medullary osmotic concentration observed during K+ depletion. Reductions in fractional reabsorption of Na+ and water in the collecting duct might result from lowered plasma aldosterone levels and the reduced medullary osmolality.
Walter
S J
SJ
Department of Physiology, Charing Cross and Westminster Medical School, London.
Shore
A C
AC
Shirley
D G
DG
D000818:Animals; D001834:Body Water / Q000378:metabolism; D005919:Glomerular Filtration Rate; D007684:Kidney Tubules / Q000503:physiopathology*; D007686:Kidney Tubules, Distal / Q000503:physiopathology; D007687:Kidney Tubules, Proximal / Q000503:physiopathology; D011188:Potassium / Q000008:administration & dosage / Q000378:metabolism; D011191:Potassium Deficiency / Q000503:physiopathology*; D051381:Rats; D012964:Sodium / Q000378:metabolism
D012964:Sodium; D011188:Potassium