Related Experiment Video
Updated: Aug 18, 2026

RNA In situ Hybridization in Whole Mount Embryos and Cell Histology Adapted for Marine Elasmobranchs
Published on: April 12, 2013
Renal sulfate secretion is carbonic anhydrase dependent in a marine teleost, Pleuronectes americanus
J L Renfro1, T H Maren, C Zeien
1Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269, USA.
Abstract:
Though chemical assays indicate that carbonic anhydrase (CA) activity is present in marine teleost nephrons, CA inhibitors have no effect on urine pH or bicarbonate excretion, parameters typically CA dependent in almost all vertebrate groups. Because marine teleost renal sulfate secretion is associated with bicarbonate anion exchange, we investigated the effect of CA inhibition on transepithelial sulfate transport by flounder renal tubule primary monolayer cultures (PTC) and on renal sulfate secretion (QSO4) by intact flounder. Both methazolamide and ethoxzolamide (10 microM) inhibited PTC secretory flux by approximately 50%; reabsorptive sulfate flux, Na-dependent glucose transport, and transepithelial electrical resistance were unaffected. A CA inhibitor restricted to the extracellular space (10 microM polyoxyethylene-aminobenzolamide, 3.7 kDa) had no effect on PTC sulfate transport. Intravenous administration of methazolamide reduced QSO4 almost 40% and had no effect on glomerular filtration rate (GFR), urine flow rate, or Pi excretion rate. Serum pH was significantly reduced 0.2 units, whereas urine pH was unchanged. Together, the in vitro and in vivo results indicate that CA facilitates renal sulfate secretion in the seawater teleost.
Related Concept Videos
Tubular Reabsorption and Secretion
Tubular reabsorption is a selective process that starts when the filtrate enters the proximal tubules. It involves substances traveling through the transcellular route (through the tubule cell and peritubular...
Reabsorption and Secretion in the PCT
Transport mechanisms involving sodium ions (Na+) contribute significantly to solute reabsorption. These mechanisms include symport and antiport processes.
A key example is the...
Reabsorption and Secretion in the DCT and Collecting Duct
The distal part of the DCT, along with the...
Renal Regulation of Acid-Base Balance
In the kidneys, cells within the proximal convoluted tubules (PCT) and the collecting ducts secrete hydrogen ions (H+) into the tubular fluid. Specifically, in the PCT, Na+/H+ antiporters secrete H+ while reabsorbing Na+.
However, the intercalated cells in...
Renal Drug Excretion: Tubular Secretion
Physiology of the Genitourinary System II: Tubular Reabsorption and Secretion

