Continuous or "pulse-and-withdraw" supply of ascorbic acid in the diet: a new approach to altering the bioavailability of ascorbic acid, using teleost fish as a scurvy-prone model
1998
Blom, J.H. | Dąbrowski, Kazimierz
In scurvy-prone animals ascorbic acid uptake is regulated by the number of intestinal "brush-border" carriers available for transport. The number of carriers is negatively affected by an increasing dietary ascorbic acid intake, thus limiting the maximum attainable uptake. We tested a new approach towards manipulating the accumulation of ascorbic acid in rainbow trout by repeatedly feeding a 10 day ascorbic acid allowance in a 1 or 3 day "pulse" followed by withdrawal, rather than spread out over the entire 10 day period. Pulse dosing led to initially increased mortalities compared to continuous dosing, but this was reversed after 55 days. Although individual weight and cumulative mortality were not significantly different after 88 days, total liver ascorbic acid levels were significantly higher in the 1-day pulse group (16.3 +/- 3.9 micrograms/g) than in the 3-day pulse (9.8 +/- 0.9 micrograms/g) or continuous (9.3 +/- 0.9 micrograms/g) groups. This led us to conclude that after an initial adaptation phase a feeding profile with intermittent ascorbic acid withdrawal results in a compensatory increase in uptake of ascorbic acid from the diet and/or a better conservation of the body pool of ascorbic acid, opening interesting new avenues for ascorbic acid dosing and therapy.
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