Abstract
Although endogenous CO2 hydration and serosal HCO 3- are both known to contribute to the high rates of intestinal HCO3- secretion important to marine fish osmoregulation, the basolateral step by which transepithelial HCO 3- secretion is accomplished has received little attention. Isolated intestine HCO3- secretion rates, transepithelial potential (TEP) and conductance were found to be dependent on serosal HCO3- concentration and sensitive to serosal DIDS. Elevated mucosal Cl- concentration had the unexpected effect of reducing HCO3- secretion rates, but did not affect electrophysiology. These characteristics indicate basolateral limitation of intestinal HCO3- secretion in seawater gulf toadfish, Opsanus beta. The isolated intestine has a high affinity for serosal HCO 3- in the physiological range (Km=10. 2mmoll1). indicating a potential to efficiently fine-tune systemic acid-base balance. We have confirmed high levels of intestinal tract expression of a basolateral Na+/HCO3- cotransporter of the electrogenic NBCeI isoform in toadfish (tfNBCel), which shows elevated expression following salinity challenge, indicating its importance in marine fish osmoregulation. When expressed in Xenopus oocytes, isolated tfNBCel has transport characteristics similar to those in the isolated tissue, including a similar affinity for HCO3- (Km=8.5mmoll- 1. Reported affinity constants of NBC1 for Na+ are generally much lower than physiological Na+ concentrations, suggesting that cotransporter activity is more likely to be modulated by HCO3- rather than Na+ availability in vivo. These similar functional characteristics of isolated tfNBCel and the intact tissue suggest a role of this cotransporter in the high HCO3- secretion rates of the marine fish intestine.
| Original language | English |
|---|---|
| Pages (from-to) | 459-468 |
| Number of pages | 10 |
| Journal | Journal of Experimental Biology |
| Volume | 213 |
| Issue number | 3 |
| DOIs | |
| State | Published - Feb 1 2010 |
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Keywords
- Acid-base balance
- Anion exchange
- Carbonic anhydrase
- SLC4
- Water absorption
ASJC Scopus subject areas
- Animal Science and Zoology
- Ecology, Evolution, Behavior and Systematics
- Molecular Biology
- Physiology
- Insect Science
- Aquatic Science
Cite this
Basolateral NBCe1 plays a rate-limiting role in transepithelial intestinal HCO3- secretion, contributing to marine fish osmoregulation. / Taylor, J. R.; Mager, E. M.; Grosell, Martin.
In: Journal of Experimental Biology, Vol. 213, No. 3, 01.02.2010, p. 459-468.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Basolateral NBCe1 plays a rate-limiting role in transepithelial intestinal HCO3- secretion, contributing to marine fish osmoregulation
AU - Taylor, J. R.
AU - Mager, E. M.
AU - Grosell, Martin
PY - 2010/2/1
Y1 - 2010/2/1
N2 - Although endogenous CO2 hydration and serosal HCO 3- are both known to contribute to the high rates of intestinal HCO3- secretion important to marine fish osmoregulation, the basolateral step by which transepithelial HCO 3- secretion is accomplished has received little attention. Isolated intestine HCO3- secretion rates, transepithelial potential (TEP) and conductance were found to be dependent on serosal HCO3- concentration and sensitive to serosal DIDS. Elevated mucosal Cl- concentration had the unexpected effect of reducing HCO3- secretion rates, but did not affect electrophysiology. These characteristics indicate basolateral limitation of intestinal HCO3- secretion in seawater gulf toadfish, Opsanus beta. The isolated intestine has a high affinity for serosal HCO 3- in the physiological range (Km=10. 2mmoll1). indicating a potential to efficiently fine-tune systemic acid-base balance. We have confirmed high levels of intestinal tract expression of a basolateral Na+/HCO3- cotransporter of the electrogenic NBCeI isoform in toadfish (tfNBCel), which shows elevated expression following salinity challenge, indicating its importance in marine fish osmoregulation. When expressed in Xenopus oocytes, isolated tfNBCel has transport characteristics similar to those in the isolated tissue, including a similar affinity for HCO3- (Km=8.5mmoll- 1. Reported affinity constants of NBC1 for Na+ are generally much lower than physiological Na+ concentrations, suggesting that cotransporter activity is more likely to be modulated by HCO3- rather than Na+ availability in vivo. These similar functional characteristics of isolated tfNBCel and the intact tissue suggest a role of this cotransporter in the high HCO3- secretion rates of the marine fish intestine.
AB - Although endogenous CO2 hydration and serosal HCO 3- are both known to contribute to the high rates of intestinal HCO3- secretion important to marine fish osmoregulation, the basolateral step by which transepithelial HCO 3- secretion is accomplished has received little attention. Isolated intestine HCO3- secretion rates, transepithelial potential (TEP) and conductance were found to be dependent on serosal HCO3- concentration and sensitive to serosal DIDS. Elevated mucosal Cl- concentration had the unexpected effect of reducing HCO3- secretion rates, but did not affect electrophysiology. These characteristics indicate basolateral limitation of intestinal HCO3- secretion in seawater gulf toadfish, Opsanus beta. The isolated intestine has a high affinity for serosal HCO 3- in the physiological range (Km=10. 2mmoll1). indicating a potential to efficiently fine-tune systemic acid-base balance. We have confirmed high levels of intestinal tract expression of a basolateral Na+/HCO3- cotransporter of the electrogenic NBCeI isoform in toadfish (tfNBCel), which shows elevated expression following salinity challenge, indicating its importance in marine fish osmoregulation. When expressed in Xenopus oocytes, isolated tfNBCel has transport characteristics similar to those in the isolated tissue, including a similar affinity for HCO3- (Km=8.5mmoll- 1. Reported affinity constants of NBC1 for Na+ are generally much lower than physiological Na+ concentrations, suggesting that cotransporter activity is more likely to be modulated by HCO3- rather than Na+ availability in vivo. These similar functional characteristics of isolated tfNBCel and the intact tissue suggest a role of this cotransporter in the high HCO3- secretion rates of the marine fish intestine.
KW - Acid-base balance
KW - Anion exchange
KW - Carbonic anhydrase
KW - SLC4
KW - Water absorption
UR - http://www.scopus.com/inward/record.url?scp=75649108493&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=75649108493&partnerID=8YFLogxK
U2 - 10.1242/jeb.029363
DO - 10.1242/jeb.029363
M3 - Article
C2 - 20086131
AN - SCOPUS:75649108493
VL - 213
SP - 459
EP - 468
JO - Journal of Experimental Biology
JF - Journal of Experimental Biology
SN - 0022-0949
IS - 3
ER -