Abstract
The role of the gastrointestinal tract in maintaining ionic homeostasis during digestion, as well as the relative contribution of the diet for providing electrolytes, has been generally overlooked in many aquatic species. An experimental diet that contained an inert reference marker (lead-glass beads) was used to quantify the net transport of Na+, K+, and Cl- during the digestion and absorption of a single meal (3% ration) by freshwater rainbow trout (Oncorhynchus mykiss). Secretion of Cl- into the stomach peaked at 8 and 12 h following feeding at a rate of 1.1 mmol·kg-1·h-1, corresponding to a theoretical pH of 0.6 in the secreted fluid (i.e., 240 mmol/l HCl). The majority (∼90%) of dietary Na+ and K+ was absorbed in the stomach, whereas subsequent large fluxes of Na+ and Cl- into the anterior intestine corresponded to a large flux of water previously observed. The estimated concentration of Na+ in fluids secreted into the anterior intestine was ∼155 mmol/l, equivalent to reported hepatic bile values, whereas the estimated concentration of Cl- (∼285 mmol/l) suggested seepage of HCl acid from the stomach in advance of the chyme front. Net absorption of K+ in the stomach occurred following the cessation of Cl- secretion, providing indirect evidence of K+ involvement with HCl acid production. Overall, 80-90% of the K+ and Cl- contents of the meal were absorbed on a net basis, whereas net Na+ absorption was negligible. Chyme-to-plasma ion concentration gradients were often opposed to the direction of ion transport, especially for Na+ and Cl-.
| Original language | English |
|---|---|
| Journal | American Journal of Physiology - Regulatory Integrative and Comparative Physiology |
| Volume | 291 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 18 2006 |
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Keywords
- Ballotini beads
- Inert markers
- Ionoregulation
- Oncorhynchus mykiss
ASJC Scopus subject areas
- Physiology
Cite this
Gastrointestinal processing of Na+, Cl-, and K + during digestion : Implications for homeostatic balance in freshwater rainbow trout. / Bucking, Carol; Wood, Chris M.
In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 291, No. 6, 18.12.2006.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Gastrointestinal processing of Na+, Cl-, and K + during digestion
T2 - Implications for homeostatic balance in freshwater rainbow trout
AU - Bucking, Carol
AU - Wood, Chris M.
PY - 2006/12/18
Y1 - 2006/12/18
N2 - The role of the gastrointestinal tract in maintaining ionic homeostasis during digestion, as well as the relative contribution of the diet for providing electrolytes, has been generally overlooked in many aquatic species. An experimental diet that contained an inert reference marker (lead-glass beads) was used to quantify the net transport of Na+, K+, and Cl- during the digestion and absorption of a single meal (3% ration) by freshwater rainbow trout (Oncorhynchus mykiss). Secretion of Cl- into the stomach peaked at 8 and 12 h following feeding at a rate of 1.1 mmol·kg-1·h-1, corresponding to a theoretical pH of 0.6 in the secreted fluid (i.e., 240 mmol/l HCl). The majority (∼90%) of dietary Na+ and K+ was absorbed in the stomach, whereas subsequent large fluxes of Na+ and Cl- into the anterior intestine corresponded to a large flux of water previously observed. The estimated concentration of Na+ in fluids secreted into the anterior intestine was ∼155 mmol/l, equivalent to reported hepatic bile values, whereas the estimated concentration of Cl- (∼285 mmol/l) suggested seepage of HCl acid from the stomach in advance of the chyme front. Net absorption of K+ in the stomach occurred following the cessation of Cl- secretion, providing indirect evidence of K+ involvement with HCl acid production. Overall, 80-90% of the K+ and Cl- contents of the meal were absorbed on a net basis, whereas net Na+ absorption was negligible. Chyme-to-plasma ion concentration gradients were often opposed to the direction of ion transport, especially for Na+ and Cl-.
AB - The role of the gastrointestinal tract in maintaining ionic homeostasis during digestion, as well as the relative contribution of the diet for providing electrolytes, has been generally overlooked in many aquatic species. An experimental diet that contained an inert reference marker (lead-glass beads) was used to quantify the net transport of Na+, K+, and Cl- during the digestion and absorption of a single meal (3% ration) by freshwater rainbow trout (Oncorhynchus mykiss). Secretion of Cl- into the stomach peaked at 8 and 12 h following feeding at a rate of 1.1 mmol·kg-1·h-1, corresponding to a theoretical pH of 0.6 in the secreted fluid (i.e., 240 mmol/l HCl). The majority (∼90%) of dietary Na+ and K+ was absorbed in the stomach, whereas subsequent large fluxes of Na+ and Cl- into the anterior intestine corresponded to a large flux of water previously observed. The estimated concentration of Na+ in fluids secreted into the anterior intestine was ∼155 mmol/l, equivalent to reported hepatic bile values, whereas the estimated concentration of Cl- (∼285 mmol/l) suggested seepage of HCl acid from the stomach in advance of the chyme front. Net absorption of K+ in the stomach occurred following the cessation of Cl- secretion, providing indirect evidence of K+ involvement with HCl acid production. Overall, 80-90% of the K+ and Cl- contents of the meal were absorbed on a net basis, whereas net Na+ absorption was negligible. Chyme-to-plasma ion concentration gradients were often opposed to the direction of ion transport, especially for Na+ and Cl-.
KW - Ballotini beads
KW - Inert markers
KW - Ionoregulation
KW - Oncorhynchus mykiss
UR - http://www.scopus.com/inward/record.url?scp=33845422570&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33845422570&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.00224.2006
DO - 10.1152/ajpregu.00224.2006
M3 - Article
C2 - 16902189
AN - SCOPUS:33845422570
VL - 291
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
SN - 0363-6143
IS - 6
ER -