Cell mechanisms of proximal tubule acidification.

RJ Alpern - Physiological reviews, 1990 - journals.physiology.org
RJ Alpern
Physiological reviews, 1990journals.physiology.org
In this review I summarize a large body of work related to the mechanism of H ion secretion
(and HC03 absorption) in the renal proximal tubule. In addition, I discuss some general
mechanisms by which transporter rate is regulated in the proximal tubule. The renal
proximal tubule is the first portion of the nephron that tubular fluid encounters after filtration
in the glomerulus. It is a high-capacity system that absorbs 50-100% of most filtered solutes
and water. The proximal tubule has classically been divided into an initial convoluted and a …
In this review I summarize a large body of work related to the mechanism of H ion secretion (and HC03 absorption) in the renal proximal tubule. In addition, I discuss some general mechanisms by which transporter rate is regulated in the proximal tubule. The renal proximal tubule is the first portion of the nephron that tubular fluid encounters after filtration in the glomerulus. It is a high-capacity system that absorbs 50-100% of most filtered solutes and water. The proximal tubule has classically been divided into an initial convoluted and a later straight tubule. Studies have generally found higher solute fluxes in the convoluted tubule compared with the straight tubule. More recently, the tubule has been divided into Sl, S2, and S3 segments based on morphology and rates of p-aminohippurate (PAH) secretion (229). In general terms, the Sl segment is the initial segment just off the glomerulus (4 mm long), and the S3 segment forms the last few millimeters of the proximal straight tubule. The major portion of the convoluted and straight tubule is comprised of the S2 segment. In this review, I concentrate on mechanisms described in the S2 segment, and where appropriate I describe evidence for axial heterogeneity (ie, differences between Sl or S3 and S2 and between convoluted and straight tubules).
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