Oxygen cost of chloride transport in perfused rectal gland ofSqualus acanthias

1980 ◽  
Vol 53 (3) ◽  
pp. 215-221 ◽  
Author(s):  
Patricio Silva ◽  
Jeffrey S. Stoff ◽  
Richard J. Solomon ◽  
Robert Rosa ◽  
Arthur Stevens ◽  
...  
Keyword(s):  
Chloride Transport ◽  
Rectal Gland ◽  
Oxygen Cost

Cyclic AMP regulation of active chloride transport in the rectal gland of marine elasmobranchs

1977 ◽  
Vol 199 (3) ◽  
pp. 443-448 ◽  
Author(s):  
Jeffrey S. Stoff ◽  
Patricio Silva ◽  
Michael Field ◽  
John Forrest ◽  
Arthur Stevens ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Chloride Transport ◽  
Rectal Gland

Identification of C-type natriuretic peptide in heart of spiny dogfish shark (Squalus acanthias)

1991 ◽  
Vol 261 (4) ◽  
pp. F734-F739 ◽  
Author(s):  
J. P. Schofield ◽  
D. S. Jones ◽  
J. N. Forrest
Keyword(s):  
Natriuretic Peptide ◽  
Chloride Transport ◽  
Marine Species ◽  
Cysteine Residue ◽  
Rectal Gland ◽  
Coding Region ◽  
Base Pairs ◽  
Partial Cdna ◽  
Primary Amino ◽  
Hormone Sensitive

An unidentified atrial natriuretic peptide (ANP)-like substance is the principal hormone regulating NaCl secretion in the shark rectal gland, an epithelial model tissue for hormone-sensitive secondary active chloride transport. Antibodies to mammalian ANP do not recognize the prohormone of marine species. The polymerase chain reaction (PCR) was used to isolate a partial cDNA encoding the shark heart natriuretic peptide. Using this partial sequence as a probe, the full-length clone [882 base pairs (bp)] was obtained from a shark heart cDNA library. Amino acids 119-135 are similar to the recently identified peptide sequences of porcine C-type natriuretic peptide (CNP) and killifish brain natriuretic peptide isolated from the brain of these species. Mature shark heart CNP terminates at the second cysteine residue and lacks a COOH-terminal extension, in contrast to cardiac ANP-like peptides of all other species. The primary amino acid sequence of the shark heart prepro-CNP is distinctly different from all other cardiac natriuretic peptides. Amplification of genomic DNA spanning the coding region produced a 1.5-kb product, indicating the presence of at least one intron. Sequencing confirmed the presence of two exons of 90 and 315 bp, separated by a 1.1-kb intron. This is the first report of a cDNA encoding in nonneuronal tissue. Elasmobranch CNP may represent a primordial form of ANP-like peptides that evolved as an adaptation to environmental osmoregulatory stress.

Mechanism of active chloride secretion by shark rectal gland: role of Na-K-ATPase in chloride transport

1977 ◽  
Vol 233 (4) ◽  
pp. F298-F306 ◽  
Author(s):  
P. Silva ◽  
J. Stoff ◽  
M. Field ◽  
L. Fine ◽  
J. N. Forrest ◽  
...  
Keyword(s):  
Chloride Transport ◽  
Sodium Concentration ◽  
Chloride Secretion ◽  
Squalus Acanthias ◽  
Rectal Gland ◽  
Tentative Hypothesis ◽  
Shark Rectal Gland ◽  
Electrochemical Equilibrium

The isolated rectal gland of Squalus acanthias was stimulated to secrete chloride against an electrical and a chemical gradient when perfused in vitro by theophylline and/or dibutyryl cyclic AMP. Chloride secretion was depressed by ouabain which inhibits Na-K-ATPase. Thiocyanate and furosemide also inhibited chloride secretion but ethoxzolamide, a carbonic anhydrase inhibitor, did not. Chloride transport was highly dependent on sodium concentration in the perfusate. The intracellular concentration of chloride averaged 70-80 meq/liter in intact glands, exceeding the level expected at electrochemical equilibrium and suggesting active transport of chloride into the cell. These features suggest a tentative hypothesis for chloride secretion by the rectal gland in which the uphill transport of chloride into the cytoplasm is coupled through a membrane carrier to the downhill movement of sodium along its electrochemical gradient. The latter is maintained by the Na-K-ATPase pump while chloride is extruded into the duct by electrical forces.

Stoichiometry of sodium chloride transport by rectal gland of Squalus acanthias

1986 ◽  
Vol 250 (3) ◽  
pp. F516-F519 ◽  
Author(s):  
P. Silva ◽  
M. A. Myers
Keyword(s):  
Sodium Chloride ◽  
Chloride Transport ◽  
Chloride Concentration ◽  
Squalus Acanthias ◽  
Salt Transport ◽  
Constant Infusion ◽  
Rectal Gland ◽  
Energetic Efficiency ◽  
Plasma Sodium ◽  
Normal Concentration

The stoichiometry of the sodium chloride cotransport system was examined in isolated perfused rectal glands of Squalus acanthias by kinetic analysis of the effect on chloride secretion of progressive substitutions of other ions for sodium and chloride in the perfusate. Secretion was stimulated by a constant infusion of dibutyryl cyclic AMP (5 X 10(-5) M) and theophylline (2.5 X 10(-4) M). Sodium was replaced by N-methyl-D-glucamine, whereas chloride was replaced by gluconate. The Km values for sodium, obtained using three different graphic methods, were close to or at the normal concentration of sodium in the plasma of the shark, suggesting that plasma sodium concentration regulates transport by the gland. The Km values for chloride were far below the normal concentration of chloride in the plasma, indicating that the chloride sites are normally saturated and therefore plasma chloride concentration cannot control transport by the gland. Hill plots revealed slopes of 1.06 for sodium and 1.6 for chloride, consistent with the hypothesis that 2 Cl- and 1 Na+ interact in the cotransport process. The cotransport linkage of 2 Cl- with 1 Na+ in the initial step of entry into the cell can be viewed as a device that doubles the energetic efficiency of salt transport, allowing 2 NaCl to be secreted for every 1 Na+ actively pumped.

Fluorescent stilbene (BADS) binding proteins in anion-transporting epithelia

1990 ◽  
Vol 259 (3) ◽  
pp. C439-C449 ◽  
Author(s):  
S. F. Pearce ◽  
J. A. Zadunaisky
Keyword(s):  
Chloride Transport ◽  
Rat Kidney ◽  
Loop Diuretics ◽  
Disulfonic Acid ◽  
Kidney Cortex ◽  
Rectal Gland ◽  
Kidney Medulla ◽  
Rat Kidney Cortex ◽  
Shark Rectal Gland ◽  
Epithelial Membranes

Chloride transport occurs at the interface between the internal and external environments of a cell where chloride uptake or efflux is regulated through a variety of mechanisms that involve cotransport of cations, exchange mechanism with anions, or movement through channels. One of these mechanisms, a chloride-bicarbonate exchange found in the human red blood cell, is well characterized and is mediated by a protein commonly known as band 3. To ascertain the presence of this or other mechanisms in epithelia, the sensitivity of epithelial membranes toward stilbenes was examined. Structure function activities of stilbene derivatives with red cell ghosts show that stilbene molecules block anion transport sites. One of these stilbenes, 4-benzamido-4'-aminostilbene-2-2'-disulfonic acid (BADS), chosen for its property of enhanced fluorescence on binding to hydrophobic sites, was used as a probe to examine the presence or absence of similar sites on epithelial membranes. With the use of nonlinear curve fitting, a single class of sites was found for BADS in the rat kidney cortex (1.6 microM), rat kidney medulla (2.1 microM), rat small intestine (2.2 microM), rat pancreatic islets (5.8 microM), frog cornea (4.3 microM), and shark rectal gland (1.5 microM). In the presence of chloride, the affinity for BADS decreased in all tissues except the frog corneal epithelium where it remained unchanged. The binding of BADS could be displaced by loop diuretics (furosemide, bumetanide, and piretanide) and thiocyanate anion in the kidney, intestine, and shark rectal gland; 50% displacement occurred at approximately 40 microM concentrations for furosemide with an order of magnitude less for bumetanide. The near-millimolar concentrations required for the displacement of BADS by loop diuretics indicate that this effect is nonspecific. However, the effect of chloride, thiocyanate, and loop diuretics on the binding of BADS indicates that BADS possibly interacts with an anion site.

The molecular basis of chloride transport in shark rectal gland.

1994 ◽  
Vol 196 (1) ◽  
pp. 405-418 ◽  
Author(s):  
J R Riordan ◽  
B Forbush ◽  
J W Hanrahan
Keyword(s):  
Cyclic Amp ◽  
Chloride Transport ◽  
Direct Action ◽  
Chloride Concentration ◽  
K Channel ◽  
Rectal Gland ◽  
Cl Secretion ◽  
Cl Channel ◽  
The Individual ◽  
Active Transport Process

Transepithelial Cl- secretion in vertebrates is accomplished by a secondary active transport process brought about by the coordinated activity of apical and basolateral transport proteins. The principal basolateral components are the Na+/K(+)-ATPase pump, the Na+/K+/2Cl- cotransporter (symporter) and a K+ channel. The rate-limiting apical component is a cyclic-AMP-stimulated Cl- channel. As postulated nearly two decades ago, the net Cl- movement from the blood to the lumen involves entry into the epithelial cells with Na+ and K+, followed by active Na+ extrusion via the pump and passive K+ exit via a channel. Intracellular [Cl-] is raised above electrochemical equilibrium and exits into the lumen when the apical Cl- channel opens. Cl- secretion is accompanied by a passive paracellular flow of Na+. The tubules of the rectal glands of elasmobranchs are highly specialized for secreting concentrated NaCl by this mechanism and hence have served as an excellent experimental model in which to characterize the individual steps by electrophysiological and ion flux measurements. The recent molecular cloning and heterologous expression of the apical Cl- channel and basolateral cotransporter have enabled more detailed analyses of the mechanisms and their regulation. Not surprisingly, since hormones acting through kinases control secretion, both the Cl- channel, which is the shark counterpart of the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator), and the cotransporter are regulated by phosphorylation and dephosphorylation. The primary stimulation of secretion by hormones employing cyclic AMP as second messenger activates CFTR via the direct action of protein kinase A (PKA), which phosphorylates multiple sites on the R domain. In contrast, phosphorylation of the cotransporter by as yet unidentified kinases is apparently secondary to the decrease in intracellular chloride concentration caused by anion exit through CFTR.

Coupled sodium and chloride transport into plasma membrane vesicles prepared from dogfish rectal gland

1978 ◽  
Vol 378 (2) ◽  
pp. 87-92 ◽  
Author(s):  
Jill Eveloff ◽  
Rolf Kinne ◽  
Eva Kinne-Saffran ◽  
Heini Murer ◽  
Patricio Silva ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Chloride Transport ◽  
Membrane Vesicles ◽  
Rectal Gland ◽  
Plasma Membrane Vesicles

Energetics of active chloride transport by shark rectal gland

1979 ◽  
Vol 10 (9) ◽  
pp. xvii
Author(s):  
F.H. Epstein ◽  
P. Suva ◽  
J. Stoff
Keyword(s):  
Chloride Transport ◽  
Rectal Gland ◽  
Shark Rectal Gland
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