Moin,
..für die Interessierten ein Stück Literatur:
Lock, E.-J., Waagbö, R., Bonga, S. W., Flik, G.,
Aquaculture Nutrition,
2010,
16, 100.
Titel:
The significance of vitamin D for fish: a review
Abstract:
Zitat:
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Fish store large quantities of vitamin D in their liver and fat tissues, including the fat associated with muscle, and this makes fish an important dietary source of vitamin D. Fish do not synthesize vitamin D and are fully dependent on dietary sources to meet their requirement. Under natural circumstances planktonic vitamin D accumulates in the aquatic food chain. In aquaculture, formulated diets are used and vitamin D intake can be manipulated. The minimum dietary requirement for vitamin D has been established in several fish species. The role of vitamin D in fish physiology is still enigmatic. Till the 1970s there was consensus that fish accumulate but not metabolize vitamin D. There is substantial evidence now, four decades later, that fish have a vitamin D endocrine system with similar functions as in mammals. We here summarize the major characteristics of the fish vitamin D endocrine system. The hydroxylation of vitamin D to more polar metabolites, their plasma levels and protein-bound transport in blood plasma will be discussed. The vitamin D receptor profile, receptor distribution and responses to vitamin D are reviewed for the key target tissues (gill, intestine, kidney and bone). We will address the classical slower actions through transcription factors as well as the faster G-protein coupled (membrane) receptor mediated effects. We then review the dietary requirement of vitamin D in aquaculture and address some lesser known functions of the vitamin D endocrine system.
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Entsprechend dem zweiten Satz sind Fische, im Gegensatz zu Säugetieren, nicht in der Lage, Vitamin D selbst herzustellen sondern benötigen zwingend Aufnahme über die Nahrungskette.
Cheers, Sandor