Rectal Gland Of Spiny Dogfish Research Articles

Natural feeding influences protein expression in the dogfish shark rectal gland: A proteomic analysis

The rectal gland is the principal salt-secreting organ in elasmobranchs, yet its functional response to normal physiological variation (e.g., due to feeding, stress) has only recently been examined. To complement studies on acid-base, digestive, and osmoregulatory physiology in response to natural feeding, we investigated protein-level responses in the rectal gland of spiny dogfish ( Squalus acanthias) 6 h, 20 h, and 5 days (reference control) after a meal. Our objective was to identify proteins involved in regulation of osmoregulatory and metabolic processes in response to feeding. Proteins were separated by two-dimensional gel electrophoresis, and protein spots that were significantly up- or down-regulated > 2 fold (i.e., abundance increased more than 100% or decreased more than 50%) were detected using gel image analysis software. Of 684 proteins analyzed on 2D gels, 16 proteins changed significantly 6 h after feeding vs. 5 day controls (5 decreased; 11 increased), and 12 proteins changed > 2 fold 20 h after feeding vs. 5 day controls (2 decreased; 10 increased). Thirteen of these proteins were identified using mass spectrometry and classified into functional pathways using the PANTHER bioinformatics database. Rectal gland proteins that were regulated following feeding fell into three main categories: cytoskeletal/muscular (e.g., tropomyosin alpha chain, transgelin), energy metabolism (e.g., malate dehydrogenase, ATP synthase), and nucleotide metabolism (nucleoside diphosphate kinase). The data also revealed that previously documented increases in the activity of isocitrate dehydrogenase after feeding are at least partially due to increased abundance of a cytosolic, NADP-dependent isoform of this enzyme. One of the primary components of the rectal gland's response to feeding appears to be maintenance of the cellular supply of energy, which would be necessary to fuel increased activities of enzymes involved in salt secretion and oxidative metabolism in the rectal gland following a meal.

Mechanism of NaCl secretion in the rectal gland of spiny dogfish (Squalus acanthias). I. Experiments in isolated in vitro perfused rectal gland tubules.

Rectal gland tubules (RGT) of spiny dogfish were dissected and perfused in vitro. Transepithelial PD (PDte), resistance (Rte), the PD across the basolateral membrane (PDbl) and intracellular chloride and potassium activities (a cell Cl-, a cell K+) were measured. In a first series, 67 RGT segments were perfused with symmetric shark "Ringers" solution. The bath perfusate contained in addition db-cAMP 10(-4), forskolin 10(-6), and adenosine 10(-4) mol X 1(-1). PDte was -11 +/- 1 (n = 67) mV lumen negative, Rte 27 +/- 2 (n = 47) omega cm2, PDbl -75 +/- 0.4 (n = 260) mV. a cell K+ and a cell Cl- were 109 +/- 22 (n = 4) and 38 +/- 4 (n = 36) mmol X 1(-1) respectively. These data indicate that Cl-secretion across the RGT must be an uphill transport process, whereas secretion of Na+ could be driven by the lumen negative PDte. Intracellular K+ is 14 mV above equilibrium with respect to the basolateral membrane PD and Cl- is 23 mV above equilibrium across the apical membrane. In series 2, the conductivity properties of the apical and basolateral membrane as well as that of the paracellular pathway were examined in concentration step experiments. Decrease of the basolateral K+ concentration led to a rapid hyperpolarization of PDbl with a mean slope of 19 mV per decade of K+ concentration change. Addition of 0.5 mmol X 1(-1) Ba2+ to the bath solution lead to a marked depolarization and abolished the response to K+ concentration steps. In the lumen a Cl- concentration downward step led to a depolarization of the lumen membrane; resulting in a mean slope of 18 mV per decade of Cl- concentration change. When dilution potentials were generated across the epithelium, the polarity indicated that the paracellular pathway is cation selective. In series 3 the equivalent short circuit current (Isc = PDte/Rte) was determined as a function of symmetrical changes in Na+ concentration, with Cl- held at 276 mmol X 1(-1), and as a function of symmetrical changes in Cl- concentration, with Na+ held at 278 mmol X 1(-1). Isc was a saturable function of Na+ concentration (Hill coefficient 0.9 +/- 0.1, K1/2 4.4 mmol X 1(-1), n = 7) and also a saturable function of Cl- concentration (Hill coefficient 2.0 +/- 0.1, K1/2 75 mmol X 1(-1), n = 11).(ABSTRACT TRUNCATED AT 400 WORDS)

Biochemical and immunological characterization of Na +, K +-ATPase from lens membrane and other tissues

Two-dimensional mapping of radioiodinated peptides from the purified α-subunit of Na +, K +-ATPase has been used to identify the α-subunit from fiber cell membrane of chick lens. Purified α-subunits from the electric organ of eel, the rectal gland of spiny dogfish, the outer medulla of dog kidney, and the chick brain all possess molecular weights of approximately 97 000. In addition, they all share at least three radioiodinated peptides in common. Two of these peptides have been localized to the C-terminal half of the molecule that is strongly associated with the lipid bilayer. The similarities of Na +, K +-ATPases from these tissues have been used to identify the α-subunit of the Na +, K +-ATPase from fiber cell membrane of chick lens. Peptide mapping of the chick lens 97 000 dalton component indicates homology with all α-subunits of all Na +, K +-ATPases studied, with closest homology with the α-subunits from chick brain. Antisera made against the purified holoenzyme of dog kidney inhibits Na +, K +-ATPase activity of both dog kidney and chick lens fiber membrane. This antisera specifically binds to components of approximately 97 000 daltons of chick lens membrane. Together, these results demonstrate that the α-subunit of Na +, K +-ATPase from chick lens membrane is comprised of polypeptides of approximately 97 000 daltons that share biochemical and antigenic homology with the Na +, K +-ATPase of other tissues and species.

The lipid composition of the electric organ of the ray, Torpedo marmorata, with specific reference to sulfatides and Na+-K+-ATPase.

The lipids from the electric organ of the ray, Torpedo marmorata, have been isolated and characterized. The major lipids were cholesterol, choline phospholipids, ethanolamine phospholipids, and sphingomyelins. The major fatty acids of ethanolamine phospholipids were 18:1, 18:0, 22:6, and 20:4. More than 50% of the acids in choline phospholipids were 16:0. The sphingomyelins consisted of five major ceramide species, all with sphingosine and the fatty acids 14:0, 15:0, 16:0, 22:1, and 24:1. The fatty acid 15:0 was mostly branched (n-2), a fatty acid earlier identified in sphingomyelins of the rectal gland of spiny dogfish. All long-chain bases were dihydroxy bases with a small percentage of branched chains. Sulfatides (cerebroside sulfate) made up the largest glycolipid fraction. The polar moiety wase galactose-3-sulfate. The fatty acids were normal and 2-hydroxy; the homologue 24:1 was the most abundant in both types of fatty acids. Most fatty acids were higher homologues of mono-unsaturated acids, but normal 18:0 fatty acid was also found. The long-chain bases were both dihydroxy and trihydroxy, with very small amounts of branched chains. The two major ceramide species of sulfatides were sphingosine combined with normal and hydroxy 24:1 fatty acids, respectively. Smaller amounts of trihydroxy base (18:0) were found linked to hydroxy 24:1 fatty acid, but not to its normal homologue. The cerebrosides contained the two major species mentioned above but lacked the trihydroxy base-hydroxy fatty acid species. The ratio of the activity of Na+-K+-dependent ATPase (EC 3.6.1.3) and the concentration of sulfatides was similar to ratios found for other tissues with normal and increased Na+ and K+ transporting capacity. The significance of this finding is discussed.

Fatty acid and aldehyde composition of major phospholipids in salt gland of marine birds and spiny dogfish.

The lipophilic components of choline phosphoglycerides and ethanolamine phosphoglycerides obtained from the salt gland of herring gull and eider duck and from the rectal gland of spiny dogfish were investigated by means of thin-layer chromatography, gas chromatography, and gas chromatography-mass spectrometry. All phospholipids analyzed were shown to contain small amounts of plasmalogens, and mainly C16, C18, and C18:1 aldehyde was detected. The fatty acids were composed of saturated, unsaturated, straight chain, and branched chain types, ranging between 14-22 carbon atoms. The lipophilic composition of the rectal gland phospholipids showed a higher degree of unsaturation and the presence of more branched chain fatty acids than that of the birds, possibly related to body temperature.

The lipid composition of the salt (rectal) gland of spiny dogfish

1. 1. The lipids from the salt (rectal) gland of spiny dogfish have been isolated and characterized. 2. 2. The major lipids were cholesterol, ethanolamine phosphoglycerides and choline phosphoglycerides. Other phospholipids were sphingomyelins, diphosphatidylglycerols, inositol phosphoglycerides and serine phosphoglycerides. The major fatty acid of ethanolamine phosphoglycerides was 22:6 with smaller amounts of 20:4, 18:1, 18:0 and 16:0. The major acids of choline phosphoglycerides were 16:0, 18:1, 20:4 and 22:6. 3. 3. The major glycosphingolipids were sulphatides and N-acetylneuraminylgalactosylglucosylceramides, and in addition there were minor amounts of glucosylceramides and galactosylceramides. 4. 4. The polar part of the sulphatides was galactose 3-sulphate. The fatty acids were mainly saturated and monounsaturated d-2-hydroxy C 22–C 24 acids. The longchain bases contained equal amounts of 1,3-dihydroxy-2-amino compounds and 1,3,4-trihydroxy-2-amino compounds with 16–20 carbon atoms. Bases with a methyl branch in Position 2, 3 or 4 from the methyl end were relatively abundant. The methyl branch was preferentially on carbon atom 16 as indicated from the polar end. 5. 5. The polar part of the choline phospholipids was phosphorylcholine exclusively. The sphingomyelin fatty acids were mainly normal C 14–C 24 acids with an unusually large amount of 22:1. A branched-chain 15:0 acid was identified, earlier unknown in sphingolipids of higher animals. All long-chain bases were dihydroxy bases with 15–19 carbon atoms. 6. 6. The unsaturation of paraffin chains was considerably higher among sphingolipids as well as glycerolipids of rectal gland of spiny dogfish (cold-blooded) than of salt gland of marine birds. Also, there was an unusually high amount of branched-chain components of sphingolipids of the rectal gland. These differences may be a prerequisite for an optimal liquid-crystalline state of the membrane. 7. 7. A role for sulphatides in Na + transport is indicated by a similar ratio of (Na +-K +)-ATPase and sulphatides in several tissues with increased transport capacity.

Sulfatides and sodium ion transport, sphingolipid composition of the rectal gland of spiny dogfish

Sulfatides and sodium ion transport, sphingolipid composition of the rectal gland of spiny dogfish