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Transepithelial electrochemical gradients in the proximal convoluted tubule during potassium depletion in the rat
Author(s) -
Shirley D. G.,
Walter S. J.,
Folkerd E. J.,
Unwin R. J.,
Bailey M. A.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.551bb.x
Subject(s) - potassium , reabsorption , chemistry , distal convoluted tubule , convoluted tubule , medicine , endocrinology , tubule , hyperkalemia , potassium deficiency , tubular fluid , cotransporter , sodium , transepithelial potential difference , potassium channel , kidney , biophysics , biochemistry , ion transporter , biology , membrane , organic chemistry
1 In order to examine the electrochemical gradient for potassium reabsorption across the S 2 segment of the proximal convoluted tubule, transepithelial potential differences and transepithelial potassium concentrations were measured in anaesthetized potassium‐replete and potassium‐depleted rats. 2 Potassium‐depleted rats were markedly hypokalaemic (plasma potassium, 1.4 ± 0.1 vs. 4.1 ± 0.1 mmol l −1 in potassium‐replete rats) and had a significantly reduced muscle potassium content. In confirmation of previous reports, glomerular filtration rate was slightly reduced, while fractional reabsorption in the proximal convoluted tubule was enhanced. 3 In potassium‐replete animals, the transepithelial potential difference (PD) at the late proximal convoluted tubule was +2.1 ± 0.3 mV (lumen positive) and the tubular fluid to plasma ultrafiltrate concentration ratio for potassium (TF K /UF K ) at the same site was 1.03 ± 0.01. In potassium‐depleted rats, there was a striking reversal of the transepithelial PD (to −4.0 ± 0.4 mV), while the TF K /UF K was increased to 1.19 ± 0.03. 4 The data from both potassium‐replete and potassium‐depleted animals are consistent with accumulating evidence that potassium reabsorption in the proximal convoluted tubule is passive in nature and depends partly on diffusion down an electrochemical gradient.