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An in vitro investigation of gastrointestinal Na(+) uptake mechanisms in freshwater rainbow trout
- Source :
- Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology. 184(8)
- Publication Year :
- 2014
-
Abstract
- In vitro gut-sac preparations of all four sections (stomach, anterior, mid, and posterior intestine) of the gastrointestinal tract (GIT) of freshwater rainbow trout, together with radiotracer ((22)Na) techniques, were used to study unidirectional Na(+) uptake rates (UR, mucosal → blood space) and net absorptive fluid transport rates (FTR) under isosmotic conditions (mucosal = serosal osmolality). On an area-specific basis, unidirectional Na(+) UR was highest in the mid-intestine, but when total gut area was taken into account, the three intestinal sections contributed equally, with very low rates in the stomach. The theoretical capacity for Na(+) uptake across the whole GIT is sufficient to supply all of the animal's nutritive requirements for Na(+). Transport occurs by low affinity systems with apparent K m values 2-3 orders of magnitude higher than those in the gills, in accord with comparably higher Na(+) concentrations in chyme versus fresh water. Fluid transport appeared to be Na(+)-dependent, such that treatments which altered unidirectional Na(+) UR generally altered FTR in a comparable fashion. Pharmacological trials (amiloride, EIPA, phenamil, bafilomycin, furosemide, hydrochlorothiazide) conducted at a mucosal Na(+) concentration of 50 mmol L(-1) indicated that GIT Na(+) uptake occurs by a variety of apical mechanisms (NHE, Na(+) channel/H(+) ATPase, NCC, NKCC) with relative contributions varying among sections. However, at a mucosal Na(+) concentration of 10 mmol L(-1), EIPA, phenamil, bafilomycin, and hydrochlorothiazide were no longer effective in inhibiting unidirectional Na(+) UR or FTR, suggesting the contribution of unidentified mechanisms under low Na(+) conditions. A preliminary model is presented.
- Subjects :
- Gill
medicine.medical_specialty
Physiology
ATPase
Fresh Water
In Vitro Techniques
Biochemistry
Models, Biological
Amiloride
chemistry.chemical_compound
Endocrinology
Osmoregulation
Furosemide
Internal medicine
medicine
Animals
Ecology, Evolution, Behavior and Systematics
Gastrointestinal tract
biology
Chemistry
Sodium Radioisotopes
Osmolar Concentration
Bafilomycin
Biological Transport
Fluid transport
Mucus
Gastrointestinal Tract
Kinetics
Hydrochlorothiazide
Oncorhynchus mykiss
biology.protein
Regression Analysis
Animal Science and Zoology
Macrolides
medicine.drug
Subjects
Details
- ISSN :
- 1432136X
- Volume :
- 184
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology
- Accession number :
- edsair.doi.dedup.....10099b3f93aef480b1bcbb787e5b6c0a