Effects of potential mediators of an intestinal brake mechanism on gut motility in Chinook salmon (Oncorhynchus tshawytscha) |
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Authors: | Forgan Leonard G Forster Malcolm E |
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Institution: | School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand. lgf16@student.canterbury.ac.nz |
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Abstract: | Potential humoral factors controlling an intestinal brake mechanism in Chinook salmon were characterised in terms of their effect on frequency and amplitude of spontaneous contractions in gastrointestinal (GI) rings. Concentration-response curves of gut contractility were produced for cholecystokinin-8 (CCK-8), gastrin-1, glucagon-like peptide-1 (GLP-1) and 5-hydroxytryptamine (5-HT) using gut rings from cardiac stomach (CS), pyloric stomach (PY), pyloric sphincter (Psp) and intestine (Int). Calculated log10 molar (M) EC50 values for CCK-8 (n=7) were: CS -8.15+/-0.90, PY -7.88+/-0.48, Psp -8.98+/-0.68, Int -8.93+/-0.64. Log10 M EC50 values calculated for gastrin 1 (n=7) were: CS -12.45+/-0.66, PY -12.55+/-0.63, Psp -9.35+/-0.78, Int -12.69+/-1.12. Log10 M EC50 values calculated for 5-HT (n=6) were: CS -4.78+/-1.05 and Psp -6.18+/-1.14. GLP -1 (n=4) produced no response in any of the tissues examined. Spontaneous contractions, measured as spikes per minute and the peak force generated were also measured for each hormone-tissue combination. The Psp generated the greatest mass-specific force, with stomach rings generating the least force. Dilutions of serum from fish diagnosed with gastric dilation air sacculitis (GDAS +ve) increased gut contractility compared to controls (GDAS -ve). |
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