ABSTRACT
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 17.2 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
17.2.1 Discovery of ascorbic acid function in fish . . . . . . . . . . . . . 256 17.3 Present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
17.3.1 Progress in AA analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 17.3.2 Presence and utilization of ascorbyl sulfate
(AAS) in fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 17.3.3 Enzymatic synthesis of ascorbyl esters . . . . . . . . . . . . . . . . 261 17.3.4 Gastric and enterointestinal ascorbate circulation . . . . . . . 262 17.3.5 Interaction of ascorbate and flavonoids . . . . . . . . . . . . . . . . 263 17.3.6 Requirement of ascorbate in fish . . . . . . . . . . . . . . . . . . . . . . 264
17.4 Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 17.4.1 Mechanism of ascorbate action . . . . . . . . . . . . . . . . . . . . . . . 266 17.4.2 Molecular (gene expression) regulation by
ascorbate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 17.4.3 Transgenic fish with GLO gene . . . . . . . . . . . . . . . . . . . . . . . 270
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
Abstract Barbara McLaren has to be credited for her 1947 discovery of ascorbic acid essentiality in teleost fish. This finding was a “scientific surprise” that was not uniformly accepted until 1969, when a study with salmonid fish demonstrated a decrease in tissue ascorbate concentration when fed a diet devoid of vitamin C. Many aspects of vitamin C metabolism in fish remain controversial today and this chapter focuses on some results obtained in salmonid fishes related to synthesis, deposition, hydrolysis, and availability of ascorbyl sulfate. Ascorbate secretion in gastric juice and reabsorption in the intestine are not unique to mammals although stomachless and stomachpossessing fish may handle ascorbate differently. The criteria for establishing ascorbate requirement in fish were reviewed and it was concluded that enormous plasticity in fish stemming from the nutritional specialization and environmental tolerance make it particularly difficult to come up with a uniform set of conditions for the purpose of comparative physiology. The mechanism of ascorbate action must include the hypothesis put forward by B. Peterkofsky and collaborators in 1991, according to which the insulin-like growth factor-binding proteins are elevated in scorbutic animals and binding to cellular receptors inhibits collagen, proteoglycan, and DNA synthesis. Studies should be continued to test a possibility of fish-to-fish (acipenserid to teleost) transfer of the gulonolactone oxidase gene through transgenic production technology.
