Postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the dorsal aorta in rainbow trout (Oncorhynchus mykiss)

Abstract

SUMMARY For the first time, changes in plasma concentrations of free amino acid(AA) and their metabolites were followed simultaneously in pre- and post-hepatic blood following a single meal in non-anaesthetized and free-swimming fish. Rainbow trout (Oncorhynchus mykiss), kept in 10°C water and fitted with cannulae in the hepatic portal vein (HPV) and the dorsal aorta (DA), were force-fed 1% of their body mass and blood samples were taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandially to follow the free AA profile. Almost all free AAs increased rapidly within the first 3 h and only a few free AAs did not change significantly over time. By 6 h, the total free AA concentration had peaked in blood taken from both the DA(7107±369 nmol ml-1) and HPV (9999±572 nmol ml-1). However, individual free AAs showed three main profiles beyond this time: for type I, a peak concentration occurred only at 6 h; for type II, there was a more gradual rise in concentration to a peak at 24 h; and for type III there were two peaks, at 6 h and 24 h. All free AAs returned to or were lower than baseline levels within 48 h, with the exception of threonine and proline. The total free AA concentrations were consistently higher (P<0.05) in the HPV than in the DA at 3 h, 6 h, 12 h and 24 h. Our data provide clear evidence that, during the first pass through the liver, hepatic modification altered individual free AA concentrations as indicated by variable ratios among the simultaneous blood samples. Furthermore, the elevation of ammonium and urea in the HPV indicates intestinal catabolism of ingested free AA before release into the HPV. In conclusion, the dual HPV and DA cannulation shows promise as a useful technique for qualitative and quantitative investigations of absorption and turnover of nutrients, especially if the measurements can be combined with reliable estimates of blood flow and labelled substances.

Digestion of a single meal affects gene expression of ion and ammonia transporters and glutamine synthetase activity in the gastrointestinal tract of freshwater rainbow trout

“…However, relative expression levels of Rhbg1 mRNA actually increased, suggesting that ammonia transport was actually being facilitated by the intestinal tissue down this large gradient. Facilitated ammonia transport in the GI tract fits with the observations of Karlsson et al (2006) that T amm was much higher in the hepatic portal vein than in the dorsal aorta following a force-fed meal in trout. The increase in Rh gene expression in the intestinal tissue corresponds to increased Rh gene expression (as well as H ?…”

“…The digestion of a typical meal has been shown to affect plasma ammonia concentrations in fish (Kaushik and Teles 1985;Wood 1993;Gelineau et al 1998;Wicks and Randall 2002;Bucking and Wood 2008;Zimmer et al 2010), doubling or even tripling concentrations beyond unfed levels, with even greater increases in the hepatic portal vein draining the intestinal circulation (Karlsson et al 2006). The excess ammonia is generated by the catalysis of dietary proteins.…”

Feed deprivation in Senegalese sole (Solea senegalensis Kaup, 1858) juveniles: effects on blood plasma metabolites and free amino acid levels

“…Therefore, sampling was performed just before daily feeding time. On the other hand, since postprandial time required to reach maximum postfeeding amino acid levels varies among individual amino acids and species (Weber and Zwingelstein 1995;Karlsson et al 2006), a 24-h fasting period was established to normalize plasma amino acid levels in fed fish and also to reach post-absorptive amino acid levels. Furthermore, fed fish were also fasted for 24 h before sampling when comparing plasma free amino acid levels under experimental conditions identical to the present study (Gillis and Ballantyne 1996;Navarro et al 1997).…”

Anaesthesia of farmed fish: implications for welfare

“…Injections of the opiate butorphanol during surgery reduced post-surgery behavioural changes, while the non-steroidal antiinflammatory drug (NSAID) ketoprofen reduced muscle tissue damage. Protocols that include both pre-anaesthetic sedation and local analgesic treatment in addition to general anaesthesia have been successfully employed in anaesthesia of salmonids undergoing surgery for insertion of dorsal aorta and portal vein cannulae (Eliason et al 2007;Karlsson et al 2006;Kiessling et al 1995Kiessling et al , 2003. Pre-anaesthetic sedation with metomidate followed by full anaesthesia with MS-222 combined with injections of lidocaine at the site of incision improved recovery in comparison with MS-222 used individually, and fish quickly resumed their normal behaviour (Eliason et al 2007;Karlsson et al 2006;Kiessling et al 1995Kiessling et al , 2003.…”