|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online May 1, 2006
Journal of Experimental Biology 209, 1883-1893 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02205
Water dynamics in the digestive tract of the freshwater rainbow trout during the processing of a single meal
McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
* Author for correspondence (e-mail: buckincp{at}mcmaster.ca)
Accepted 13 March 2006
The temporal effects of feeding and digestion on chyme composition,
specifically water and solid content, and net fluxes across the
gastrointestinal tract, as well as plasma parameters, were examined in
freshwater rainbow trout. A single meal of commercial dry pellets,
incorporating ballotini beads as inert reference markers, was employed. Plasma
Na+ levels increased by 15–20% at 2 h post-feeding, where
Cl– levels did not change. Plasma osmolality was well
regulated despite an initial chyme osmolality (775 mOsm) 2.8-fold higher than
that in the blood plasma. Chyme osmolality throughout the gastrointestinal
tract remained significantly higher than plasma osmolality for the duration of
the 72 h period. Solid material was absorbed along the entire intestinal
tract, although not in the stomach, necessitating the incorporation of an
inert marker. A similar temporal pattern of transit between the ballotini
beads (solid phase marker) and 3[H]-PEG 4000 (fluid phase marker),
provided support for the use of ballotini beads. Large additions of water to
the chyme were seen in the stomach, the largest occurring within 2 h following
feeding (7.1±1.4 ml kg–1), and amounted to 
16 ml
kg–1 over the first 12 h. As the chyme entered the anterior
intestine, a further large water secretion (3.5±0.5 ml
kg–1) was seen. Thereafter the water fluxes into the chyme of
the anterior intestine decreased steadily over time, but remained positive,
whereas the mid-intestine exhibited net absorption of water at all time
points, and the posterior intestine demonstrated little water handling at any
time. The endogenous water that was secreted into the anterior intestine was
absorbed along the tract, which showed a net water flux close to zero.
However, assuming that the water secreted into the stomach was endogenous in
nature, the processing of a single meal resulted in net loss of endogenous
water (0.24 ml kg–1 h–1) to the environment,
a beneficial consequence of the osmotic challenge offered by the food for a
freshwater hyperosmotic regulator.
Key words: ballotini bead, 3[H]-PEG 4000, chyme, gastrointestinal tract, inert marker, osmolality, rainbow trout, Oncorhynchus mykiss
This article has been cited by other articles:
|
|
 |
|
  C. M. Wood, M. Kajimura, C. Bucking, and P. J. Walsh Osmoregulation, ionoregulation and acid-base regulation by the gastrointestinal tract after feeding in the elasmobranch (Squalus acanthias) J. Exp. Biol., April 15, 2007; 210(8): 1335 - 1349. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Bucking and C. M. Wood Gastrointestinal processing of Na+, Cl-, and K+ during digestion: implications for homeostatic balance in freshwater rainbow trout Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2006; 291(6): R1764 - R1772. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. J. McGaw Feeding and digestion in low salinity in an osmoconforming crab, Cancer gracilis II. Gastric evacuation and motility J. Exp. Biol., October 1, 2006; 209(19): 3777 - 3785. [Abstract] [Full Text] [PDF]
|
|
