Is the Alkaline Tide a Signal to Activate Metabolic or Ionoregulatory Enzymes in the Dogfish Shark (Squalus acanthias)?

2008 ◽  
Vol 81 (3) ◽  
pp. 278-287 ◽  
Author(s):  
Chris M. Wood ◽  
Makiko Kajimura ◽  
Thomas P. Mommsen ◽  
Patrick J. Walsh
Keyword(s):  
Squalus Acanthias ◽  
Alkaline Tide ◽  
Dogfish Shark

scholarly journals The alkaline tide goes out and the nitrogen stays in after feeding in the dogfish shark, Squalus acanthias

2007 ◽  
Vol 159 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Chris M. Wood ◽  
Carol Bucking ◽  
John Fitzpatrick ◽  
Sunita Nadella
Keyword(s):  
Squalus Acanthias ◽  
Alkaline Tide ◽  
Dogfish Shark

Characterization of an endothelin ET(B) receptor in the gill of the dogfish shark Squalus acanthias

1999 ◽  
Vol 202 (24) ◽  
pp. 3605-3610 ◽  
Author(s):  
D.H. Evans ◽  
M.P. Gunderson
Keyword(s):  
Blood Vessels ◽  
Gill Tissue ◽  
Squalus Acanthias ◽  
Single Site ◽  
Acid Base Balance ◽  
Ion Regulation ◽  
Base Balance ◽  
Dogfish Shark ◽  
Kinetics Of

Endothelins (ETs) are potent vasoconstrictive peptides that are secreted by the vascular endothelium and other tissues in vertebrates. Previous studies have demonstrated that ETs are expressed in a variety of fish tissues and contract various blood vessels. In order to determine if receptors for ET are expressed in fish gill tissue, we examined the binding kinetics of (125)I-labeled, human ET-1 to membrane fragments isolated from the gill of the dogfish shark, Squalus acanthias. (125)I-ET-1 bound at a single site, with a dissociation constant (K(d)) and binding site number (B(max)) very similar to those described in a variety of mammalian blood vessels. ET-1 and ET-3 competed equally with (125)I-ET-1, suggesting that the receptor was ET(B), which has been shown in mammalian systems to bind to both ligands equally. The ET(B)-specific agonists sarafotoxin S6c, IRL-1620, and BQ-3020 also competed against (125)I-ET-1 at a single site, supporting this hypothesis. We conclude that the shark gill expresses an ET(B) receptor with substantial homology to the mammalian receptor and that ET may play an important role in modulating such vital gill functions as gas exchange, ion regulation, acid-base balance, and excretion of nitrogen.

Fluorescein-methotrexate transport in dogfish shark (Squalus acanthias) choroid plexus

2006 ◽  
Vol 291 (2) ◽  
pp. R464-R472 ◽  
Author(s):  
Carsten H. Baehr ◽  
Gert Fricker ◽  
David S. Miller
Keyword(s):  
Protein Kinase ◽  
Choroid Plexus ◽  
Organic Anion ◽  
Basolateral Membrane ◽  
Fold Increase ◽  
Squalus Acanthias ◽  
Cellular Accumulation ◽  
Vascular Space ◽  
Dogfish Shark ◽  
Tissue Compartments

The vertebrate choroid plexus removes potentially toxic metabolites and xenobiotics from cerebrospinal fluid (CSF) to blood for subsequent excretion in urine and bile. We used confocal microscopy and quantitative image analysis to characterize the mechanisms driving transport of the large organic anion, fluorescein-methotrexate (FL-MTX), from bath (CSF-side) to blood vessels in intact lateral choroid plexus from dogfish shark, Squalus acanthias, an evolutionarily ancient vertebrate. With 2 μM FL-MTX in the bath, steady-state fluorescence in the subepithelium/vascular space exceeded bath levels by 5- to 10-fold, and fluorescence in the epithelial cells was slightly below bath levels. FL-MTX accumulation in both tissue compartments was reduced by NaCN, Na removal, and ouabain, but not by a 10-fold increase in medium K. Certain organic anions, e.g., probenecid, MTX, and taurocholate, reduced FL-MTX accumulation in both tissue compartments; p-aminohippurate and estrone sulfate reduced subepithelial/vascular accumulation, but not cellular accumulation. At low concentrations, digoxin, leukotriene C4, and MK-571 reduced fluorescence in the subepithelium/vascular space while increasing cellular fluorescence, indicating preferential inhibition of efflux over uptake. In the presence of 10 μM digoxin (reduced efflux, enhanced cellular accumulation), cellular FL-MTX accumulation was specific, concentrative, and Na dependent. Thus transepithelial FL-MTX transport involved the following two carrier-mediated steps: electroneutral, Na-dependent uptake at the apical membrane and electroneutral efflux at the basolateral membrane. Finally, FL-MTX accumulation in both tissue compartments was reduced by phorbol ester and increased by forskolin, indicating antagonistic modulation by protein kinase C and protein kinase A.

Control of rectal gland secretion by blood acid–base status in the intact dogfish shark (Squalus acanthias)

2007 ◽  
Vol 156 (2) ◽  
pp. 220-228 ◽  
Author(s):  
Chris M. Wood ◽  
R. Stephen Munger ◽  
Jill Thompson ◽  
Trevor J. Shuttleworth
Keyword(s):  
Squalus Acanthias ◽  
Gland Secretion ◽  
Rectal Gland ◽  
Acid Base ◽  
Acid Base Status ◽  
Dogfish Shark
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