Ion-motive ATPases and active, transbranchial NaCl uptake in the red freshwater crab, Dilocarcinus pagei (Decapoda, Trichodactylidae)

Autor(en): Weihrauch, D
McNamara, JC
Towle, DW
Onken, H
Stichwörter: Biology; CARCINUS-MAENAS; concanamycin; crab; Dilocarcinus pagei; ERIOCHEIR-SINENSIS; EURYHALINE CRABS; EXCRETION; gill epithelia; H+-ATPASE; Life Sciences & Biomedicine - Other Topics; MACROBRACHIUM-OLFERSII DECAPODA; NA++K+-ATPASE; Na+/K+-ATPase; NaCl uptake; osmoregulation; ouabain; phylogenetic analysis; POSTERIOR GILLS; PROTEIN; short-circuit current; transepithelial voltage; V-ATPASES; V-type H+-ATPase
Erscheinungsdatum: 2004
Volumen: 207
Ausgabe: 26
Startseite: 4623
Seitenende: 4631
The present investigation examined the microanatomy and mRNA expression and activity of ion-motive ATPases, in anterior and posterior gills of a South American, true freshwater crab, Dilocarcinus pagei. Like diadromous crabs, the anterior gills of this hololimnetic trichodactylid exhibit a highly attenuated (2-5 mum), symmetrical epithelium on both lamellar surfaces. In sharp contrast, the posterior gill lamellar epithelia are markedly asymmetrical. Their proximal side consists of thick (18-20 mum) cells, displaying features typical of a transporting epithelium, while the distal epithelium is thin (3-10 mum) and formed entirely by apical pillar cell flanges. Both anterior and posterior gills express Na+/K+- and V-ATPases. Phylogenetic analysis of partial cDNA sequences for the Na+/K+-ATPase alpha-subunit and V-ATPase B-subunit among various crab species confirmed the previous classification and grouping of D. pagei based on morphological criteria. Semi-quantitative RT-PCR clearly showed that mRNA for both ion pump subunits is more intensely expressed in posterior gills. Na+/K+-ATPase activity in the posterior gills was nearly fourfold that of anterior gills, while V-ATPase and F-ATPase activities did not differ. A negative short-circuit current (I-sc) was measured using the distal side of split, posterior gill lamellae, mounted in a modified Ussing chamber and perfused symmetrically with identical hemolymph-like salines. Although hemolymph-side ouabain did not affect this current, concanamycin significantly reduced I-sc without altering preparation conductance, suggesting V-ATPase-driven Cl- absorption on the distal side of the posterior gill lamellae, as known to occur in diadromous crabs adapted to freshwater. These findings suggest that active Na+ uptake predominates across the thick proximal epithelium, and Cl- uptake across the thin, distal epithelium of the posterior gill lamellae.
ISSN: 00220949
DOI: 10.1242/jeb.01333

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