Bicarbonate reabsorption by the amphibian nephron

Document Type

Article

Publication Date

1986

Publication Title

American Journal of Physiology - Renal Physiology

Volume

251

Issue

5

Abstract

To determine the site of bicarbonate reabsorption, tubular fragments from five different segments of the salamander nephron (Ambystoma) were perfused in vitro. Bicarbonate contents (total CO2) of tubular fluid were determined by microcalorimetry. Bicarbonate was not transported by the diluting segment or the mid-distal tubule. Although proximal tubule fragments did appear to reabsorb bicarbonate (10.8 +/- 3.7 pmol X mm-1 X min-1, P less than 0.01, n = 14), the chemical gradients observed were small with respect to the sensitivity of our methods. In the late distal tubule (LDT), bicarbonate reabsorption averaged 28.9 +/- 8.2 pmol X mm-1 X min-1 (P less than 0.01, n = 16). Transport in this segment was inhibited by ethoxzolamide or by perfusing with a sodium-free solution. Ethoxzolamide had no effect on the trans-epithelial voltage. Thus bicarbonate is reabsorbed by the LDT of amphibia via a mechanism that is dependent on carbonic anhydrase and the presence of luminal sodium. The 13 initial collecting tubules (ICT) studied did not appear to reabsorb bicarbonate. On the other hand, some ICT developed substantial bicarbonate gradients. Therefore this nephron segment has the capacity to reabsorb bicarbonate.

Keywords

Acid-base imbalances; Amphibians – Physiology; Kidney tubules; Renal function; Salamanders

Disciplines

Animal Sciences | Animal Structures | Biochemistry, Biophysics, and Structural Biology | Nephrology | Physiology

Language

English

Permissions

Use Find in Your Library, contact the author, or use interlibrary loan to garner a copy of the article. Publisher copyright policy allows author to archive post-print (author’s final manuscript). When post-print is available or publisher policy changes, the article will be deposited


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