Environmental salinity regulates receptor expression, cellular effects, and circulating levels of two antagonizing hormones, 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3, in rainbow trout.

In freshwater-adapted rainbow trout, intestinal cells (enterocytes) possess receptors for 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] in the basolateral membrane, and respond to treatment with 1,25(OH)(2)D(3) with increased intracellular calcium concentrations. No receptors are found for the antagonizing hormone 24,25-dihydroxyvitamin D(3) [24,25(OH)(2)D(3)] at the enterocyte basolateral membrane, and it has no effect on enterocyte calcium homeostasis. After acclimation to seawater, however, the enterocyte membrane receptors for 1,25(OH)(2)D(3) are down-regulated and specific binding for 24,25(OH)(2)D(3) appears, which is further up-regulated with time spent in seawater. This shift in receptor expression is concurrent with an increased sensitivity of the enterocytes to 24,25(OH)(2)D(3) and a decreased sensitivity to 1,25(OH)(2)D(3). This results in a partial inhibition of intracellular calcium uptake, which would be beneficial when inhabiting a calcium-rich environment like seawater.

Nemere, Ilka (author)
Aksnes, Lage (author)
Sundell, Kristina,1959Gothenburg University,Göteborgs universitet,Zoologiska institutionen,Department of Zoology(Swepub:gu)xskris (author)
Göteborgs universitetZoologiska institutionen (creator_code:org_t)

By the author/editor: Larsson, D; Nemere, Ilka; Aksnes, Lage; Sundell, Kristin ...

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