Im. Soaresdasilva et al., L-3,4-DIHYDROXYPHENYLALANINE (L-DOPA) IN ANODONTA-CYGNEA - VARIATION WITH ACIDOSIS, Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 120(3), 1998, pp. 463-468
L-3,4-dihydroxyphenylalanine is present in the shell, mantle cells and
fluids of the bivalve Anodonta cygnea. Normal conditions, representin
g autumn and winter period, present high levels of L-DOPA in the fluid
s and low levels in the mantle. However, data show that there is a dif
ferent distribution of this compound all over the mantle area, and the
portions with the most significant L-DOPA content are the siphon bord
er and the mantle part adjacent to the curvature of the shell (next to
the umbo). Acidic conditions, simulating internal acidosis that occur
s in Anodonta cygnea during spring and summer, show a significant vari
ation of L-DOPA, increasing in the mantle, mainly in the central part,
and decreasing in the fluids. Moreover, results indicate that L-DOPA
contributes to the formation of the pellicle formed under acidosis in
the nacreous layer. These variations of L-DOPA with acidosis suggest t
hat its synthesis is increased in the central mantle and all available
L-DOPA is removed from the fluids to integrate the thin pellicle form
ed in the nacreous layer of the shell. The recently formed periostracu
m and the umbo have the highest L-DOPA content in the shell because th
ey are sclerotized structures. These results suggest that the biominer
alization and sclerotization processes of the shell are closely relate
d to the integration of L-DOPA in the nacreous layer and in the perios
tracum, respectively. The decrease of the internal pH appears as a rel
evant switch to induce the production of this amino acid in the centra
l mantle. (C) 1998 Elsevier Science Inc. All rights reserved.