| Summary: | 碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 99 === The objective of this study was to investigate the folate metabolism in hybrid tilapia with a modified cannulated urine collector through 24-hour changes of plasma, urine and organ accumulation of folate and its main metabolite (5-methyl tetrahydrofolate(5-MTF)) concentration at various sampling time points after the supplementation of exogenous folate sources either by oral administration or by injection.
The urine and plasma folate concentrations were peaked at 4 through 8 hours and the plasma 5-MTF concentrations were peaked between 12th and 24th hour after fish were orally administrated diets containing various levels of folate. Organ folate accumulation were found the highest in the liver of fish fed a diet containing 20 ppm of folate and in the spleen of fish fed a diet containing 8 ppm of folate. But there were no significant differences found among the all oral treatment levels of folate on the muscle of folate (170.9 - 178.9 ppb) and 5-MTF (206.3 - 216.5 ppb) concentrations. The plasma folate concentrations were peaked at 2 through 4 hours and the plasma 5-MTF concentrations were peaked between 6th and 12th hour after fish injected different levels of folic acid. Organ folate accumulation were found the highest in the liver of fish injected 3.2 ppm of folate and in the spleen of fish injected 1.6ppm of folate. However, there were no significant differences found among the all injected levels of folate on the concentrations of folate (175.6 - 184.8 ppb) and 5-MTF (212.9 - 224.8 ppb) in the muscle.
A linear relationship of the plots of the amount of urine folate against plasma folate indicated that the excretion rate must be positively correlated to the level of oral input. The positive linear correlation of the plots of the amount of folate against the amount of 5-MTF in the plasma, liver and spleen except muscle were attributive to the amount of folate input either from food or vein injection.
The significant increase in the unknown amount of folate through ADME analyses reflected either from the fish orally administrated 20ppm dietary folate or 3.2 ppm injected level revealed that dietary or injected levels exceeded 8 or 1.6 ppm must have effectively reduced folate absorption ability of the small intestine of hybrid tilapia. Hence, when exogenous supply of folate exceeds certain level, organs and tissues other than liver, kidney may play alternative accumulation role in folate metabolism of tilapia.
Current study revealed that exogenous supplementation of folate not only increased the amount of folate accumulation but also elevated the amount of folate metabolite, the 5-MTF (a monocarbon carrier), in the fish body. It was concluded that oral level of 8 ppm and injection level of 1.6 ppm folate would reach a saturated level of folate accumulation in fish body.
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