S187Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S171–S188

intestine, previously perfused with a clay containing solution.Even though kaolinite consumption appeared heterogeneous,histological observations revealed a significant increase in thethickness of the villi caused by large vacuoles at the base ofthe absorptive cells. Other morphological changes include alengthening of the apical microvilli and an increasedmitochondrial replication. Furthermore, significant increaseswere observed in the absorption of LCFAs after intestinalperfusion with clay solution, and in the expression of fattyacid binding protein (FABP) after 28 days of kaoliniteingestion.These results indicate that animals can benefit from claycomplementation when available. This ingestion stimulates theabsorption of LCFAs most probably through endocytosis andtheir rapid binding by FABP. This can act as an intracellularbuffer to prevent fat reflux into the intestinal lumen. Never-theless, blood aluminum levels appeared higher in clay-eatingrats compared to the control group, indicating that kaolinite isdissociated in the lumen, and that aluminum passes directlythrough the intestinal barrier.

doi:10.1016/j.cbpa.2007.01.408

A12.50Validation of the hepatic portal vein cannulation techniqueusing Atlantic salmon (Salmo salar L.)

E. Eliason, A. Farrell, (University of British Columbia); A.Kiessling, A. Karlsson, B. Djordjevic (Norwegian Universityof Life Sciences)

Cannulation of the hepatic portal vein in fish is potentially avaluable technique for both fish nutritionists and physiolo-gists. Combining dorsal aorta and hepatic portal veincannulation techniques enables the examination of nutrientuptake and hepatic metabolic transformation, as well assystemic physiological changes associated with gut function(such as acid–base balance and ion and osmotic regulation) ingreater detail than previously possible. This study assessedthe hepatic portal vein cannulation technique and subsequentrecovery from surgery in Atlantic salmon (Salmo salar L).Within the 1- to 3-day post-surgery period, hematocrit levelswere maintained and blood variables, including cortisol,returned to baseline levels, indicating that this technique is aviable and useful method to study the digestive physiology offish. We also report on the appearance profiles for aminoacids in blood sampled simultaneously from the hepatic portalvein and dorsal aorta following a meal to illustrate thedifferential effects of liver metabolism on the amino acidprofiles for pre- and post-hepatic blood samples. Supportedby NSERC Canada and the Norwegian Research Councilcenter of excellence, Aquaculture Protein Centre (APC).

doi:10.1016/j.cbpa.2007.01.409

A12.51Influence of water salinity and altitude on the tolerance ofamphibian early life stages to nitrite

C. Shinn, A. Marco, (Estación Biológica de Doñana);L. Serrano, (Universidad de Sevilla)

High concentrations of nitrite in aquatic environments are toxicfor a number of amphibian species. Chloride ions are known topartially inhibit nitrite (NO2

−) toxicity in saltwater fish and arehypothesised to do the same in amphibians. Newly hatchedtadpoles of Bufo calamita, Rana perezi and Hyla meridionalisfrom Doñana National Park (DNP; altitude 20 m) and Ranaperezi from Gredos Mountains (altitude 1900 m) were subjectedto a series of sodium nitrite (NaNO2) concentrations (0–20 mgN-NO2-/L) for up to 20 days.By day 8 at 5 mg/L N-NO2

− all R. perezi larvae from DNPwere dead whilst Bufo calamita larval mortality rates wereconsiderably lower at that concentration after 15 days ofexposure. However, at day 15 no deaths were registered at5 mg/L N-NO2

− for H. meridionalis and at 20 mg/L N-NO2−

this species presented intermediate mortality rates. R. perezilarvae from Gredos Mountains displayed an LC50 below0.5 mg N-NO2

−/L after 16 days of exposure.Eggs and tadpoles of all three species were subjected a series ofnitrite concentrations in brackish water. The presence of Cl−

ions increased survival, activity and growth of larvae exposed tonitrite.Rana perezi populations living at altitude appear to besignificantly more sensitive to NO2

− pollution than coastalpopulations, although variation in temperature and initialdevelopmental stage may explain some of this variation. Lowsalinity levels appear to attenuate the toxicity of nitrite todeveloping amphibians. This finding has ecological signifi-cance for endangered species of amphibians living in brackishconditions.

doi:10.1016/j.cbpa.2007.01.410

A12.52Sexual dimorphism of muscle growth in a large flatfish, theAtlantic halibut (Hippoglossus hippoglossus L.)

Ø. Hagen, V. Vieira, I. Johnston, (University of St. Andrews);C. Solberg, (Bodø University College)

Atlantic halibut (Hippoglossus hippoglossus L.) is an importantfood fish that can reach >100 kg in the wild. It is currently beingfarmed on a small scale in several countries including Scotland,Norway and Iceland. For large flatfish species, such as halibut,the large number of muscle fibres present and potentialdifferences in muscle cellularity between dorsal and ventraland left and right sides of the trunk complicate studies of musclegrowth. In the present study, 22 wild and farmed halibut werestudied ranging from 2 to 97.000 g. Statistical methods for thedetermination of maximum fibre number (FNmax) are described,