Document Detail

Renal tubular transport of organic acids. Studies with oxalate and para-aminohippurate in the rat.
MedLine Citation:
PMID:  641156     Owner:  NLM     Status:  MEDLINE    
The renal handling of oxalate was examined by free-flow micropuncture, intratubular microinjection, and droplet precession techniques in the rat. After the sustained i.v. infusion of [(14)C]oxalate, the fractional delivery of oxalate from the early portions of the proximal tubule was 120.1+/-4.4%, indicating net secretion. Fractional delivery rates from the late proximal tubule (124.6+/-6.1), distal tubule (120.9+/-2.9), and final urine (126.2+/-2.9%) were not different from that of the early proximal tubule. Direct intratubular microinjections of oxalate into the early proximal tubule and late proximal tubule yielded urinary recovery rates of 85+/-3% and 101+/-2%, respectively, suggesting that oxalate absorption does occur in the mid-portions of the proximal tubule. Droplet precession studies confirmed a secretory flux for oxalate. In contrast to oxalate, para-aminohippurate (PAH), the more traditional marker for organic acid transport, was secreted in the late portions of the proximal tubule and in large measure at a site between the late proximal and distal tubules, presumably the pars recta. Probenecid inhibited PAH secretion but was without effect on net oxalate transport, oxalate absorption, or oxalate secretion. These studies demonstrate that net oxalate secretion occurs in the early portions of the proximal convoluted tubule, undergoes bidirectional transport of approximately equal magnitude in later segments of the proximal tubule, and probably is not transported in more distal nephron sites. The secretory mechanism for oxalate differs from that of PAH in that it is located in a different segment of the nephron and is not inhibited by probenecid. These differences suggest that the early portions of the proximal tubule are important in the renal metabolism of some organic acids.
E J Weinman; S J Frankfurt; A Ince; S Sansom
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  The Journal of clinical investigation     Volume:  61     ISSN:  0021-9738     ISO Abbreviation:  J. Clin. Invest.     Publication Date:  1978 Mar 
Date Detail:
Created Date:  1978-06-12     Completed Date:  1978-06-12     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7802877     Medline TA:  J Clin Invest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  801-6     Citation Subset:  AIM; IM    
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MeSH Terms
Aminohippuric Acids / metabolism*
Biological Transport
Kidney Tubules / metabolism*
Kidney Tubules, Distal / metabolism
Kidney Tubules, Proximal / metabolism
Metabolic Clearance Rate
Oxalates / administration & dosage,  metabolism*
p-Aminohippuric Acid / administration & dosage,  metabolism*
Reg. No./Substance:
0/Aminohippuric Acids; 0/Oxalates; 61-78-9/p-Aminohippuric Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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