Potassium channels in the basolateral membrane of the rectal gland of the dogfish (Squalus acanthias)

The morphology of the rectal gland was examined in spiny dogfish ( Squalus acanthias L, 1758) sharks fasted (1 week) or 6 and 20 h postfeeding. The morphology of the fasted gland showed a pattern reflecting a dormant physiology, with thick gland capsule, thick stratified epithelium, and secretory parenchyma with tubules of small diameter and lumen. The secretory cells of the tubular epithelium were enlarged and irregularly shaped with abnormally condensed or highly vacuolized cytoplasm containing numerous lysosomes. Early-stage apoptotic cells were not uncommon. Secretory cells showed signs of low activity, e.g., mitochondria with weakly stained matrix and small cristae, poorly branched infoldings of basolateral membranes, and microvesicle-free subapical cytoplasm. All characteristics examined changed significantly upon feeding, consistent with increased salt and fluid secretion: the outer capsule muscle layer and the stratified epithelium decreased in diameter; the tubules enlarged; the secretory cells showed extensive development of the basolateral membrane, more mitochondria, and abundant apical microvesicles. Secretory cell apical surface was increased. The minor differences between morphology in 6 and 20 h postfeeding indicated that changes took place rapidly and were complete by 6 h. Our results are discussed in the context of prior studies of metabolism, proteomics, and cellular pathways of gland activation.

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Resolution of apical from basolateral membrane of shark rectal gland

AJP Cell Physiology ◽

10.1152/ajpcell.1986.251.5.c721 ◽

1986 ◽

Vol 251 (5) ◽

pp. C721-C726 ◽

Cited By ~ 12

Author(s):

W. P. Dubinsky ◽

L. B. Monti

Keyword(s):

Membrane Fraction ◽

Sucrose Gradient ◽

Apical Membrane ◽

Specific Activity ◽

Basolateral Membrane ◽

Anion Transport ◽

Squalus Acanthias ◽

Rectal Gland ◽

Crude Homogenate ◽

Shark Rectal Gland

Membrane fractions were isolated from the rectal gland of Squalus acanthias using differential centrifugation and a sucrose gradient run in the presence of 1 M KBr. Using the basolateral membrane marker Na+-K+-ATPase, we obtained a sixfold purification with the most highly purified fraction from the gradient (sp act = 336 +/- 37 mumol X mg protein-1 X h-1). Electrogenic Br- transport was used as a marker activity of the apical membrane, which enabled the identification and purification of a membrane fraction that is highly resolved from the basolateral membrane. The most active fraction was purified approximately 50-fold compared with the crude homogenate. In this fraction, the specific activity of electrogenic anion transport was 296 +/- 87 nmol X mg protein-1 X min-1, whereas the ATPase was only 17.6 +/- 5.7 mumol X mg protein-1 X h-1, representing about a 4-5% contamination of the apical fraction with the basolateral membrane.

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Active potassium transport coupled to active sodium transport in vesicles reconstituted from purified sodium and potassium ion-activated adenosine triphosphatase from the rectal gland of Squalus acanthias

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)41066-1 ◽

1975 ◽

Vol 250 (16) ◽

pp. 6296-6303

Author(s):

S Hilden ◽

LE Hokin

Keyword(s):

Sodium Transport ◽

Adenosine Triphosphatase ◽

Potassium Transport ◽

Potassium Ion ◽

Squalus Acanthias ◽

Rectal Gland ◽

Active Sodium ◽

Active Sodium Transport ◽

Sodium And Potassium

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Molecular properties of purified (sodium + potassium)-activated adenosine triphosphatases and their subunits from the rectal gland of Squalus acanthias and the electric organ of Electrophorus electricus

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)41403-8 ◽

1975 ◽

Vol 250 (11) ◽

pp. 4178-4184

Author(s):

JR Perrone ◽

JF Hackney ◽

JF Dixon ◽

LE Hokin

Keyword(s):

Electric Organ ◽

Squalus Acanthias ◽

Molecular Properties ◽

Rectal Gland ◽

Sodium Potassium ◽

Electrophorus Electricus ◽

Adenosine Triphosphatases

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Osmoregulation by the Prenatal Spiny Dogfish, Squalus Acanthias

Journal of Experimental Biology ◽

10.1242/jeb.101.1.295 ◽

1982 ◽

Vol 101 (1) ◽

pp. 295-305 ◽

Cited By ~ 4

Author(s):

DAVID H. EVANS ◽

AIMO OIKARI ◽

GREGG A. KORMANIK ◽

LEIGH MANSBERGER

Keyword(s):

Sea Water ◽

Electrical Potential ◽

Fluid Flows ◽

Maternal Plasma ◽

Water Levels ◽

Squalus Acanthias ◽

Rectal Gland ◽

Na Efflux ◽

Uterine Fluid ◽

Electrochemical Equilibrium

Late in gestation of the ovoviviparous dogfish, Squalus acanthias, the uterine fluids are essentially sea water, while the plasma of the ‘pup’ is similar to that of the female, i.e. isotonic to sea water/uterine fluids, with significantly less Na and Cl, and substantial concentrations of urea. Early ‘candle’ embryos are bathed in ‘candle’ fluid and uterine fluid which contains Na and Cl concentrations intermediate between maternal plasma and sea water levels, K concentrations above sea water levels, and urea concentrations slightly below those found in the maternal plasma. Both fluids are isotonic to sea water and maternal plasma. Incubation of ‘candles’ with associated embryos in sea water for 4–6 days resulted in significant increases in ‘candle’ fluid Na and Cl concentrations, and a decline in ‘candle’ fluid K and urea levels. However, under these conditions, the ‘candle’ embryo is still able to regulate plasma Na, Cl, K and urea concentrations. The efflux of Cl is approximately 5 times the efflux of Na from the prenatal ‘pup’; however, both effluxes are equivalent to those described for adult elasmobranchs. The transepithelial electrical potential (TEP) across the ‘pup’ is −4.4 mV in sea water, which indicates that both Na and Cl are maintained out of electrochemical equilibrium. Cloacal fluid flows vary diurnally with Na and Cl concentrations significantly above those of the plasma. Rectal gland efflux can account for 50–100% of the Na efflux, but less than 25% of the Cl efflux. Removal of the rectal gland resulted in an increase in plasma Na and Cl concentrations 48 or 72 h after the operation, but in both cases it appears that some extra rectal gland excretory system balances at least some of the net influx of both salts. Our results demonstrate that even very young ‘candle’ embryos of S. acanthias are capable of osmoregulation, and that older embryos (‘pups') osmoregulate against sea water intra-utero and display the major hallmarks of elasmobranch osmoregulation, including a reduced ionic permeability and a functional rectal gland for net extrusion of NaCl. In addition, it appears that other pathways exist for salt extrusion in addition to the rectal gland. Note:

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Neural control of shark rectal gland

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1988.255.2.r212 ◽

1988 ◽

Vol 255 (2) ◽

pp. R212-R216 ◽

Cited By ~ 2

Author(s):

J. S. Stoff ◽

P. Silva ◽

R. Lechan ◽

R. Solomon ◽

F. H. Epstein

Keyword(s):

Neural Control ◽

Squalus Acanthias ◽

Rectal Gland ◽

Channel Blockers ◽

Stimulatory Action ◽

Histological Techniques ◽

Neuronal Tissue ◽

Neural Modulation ◽

Veratrum Alkaloids ◽

Gland Function

Veratrum alkaloids stimulated salt secretion by the isolated perfused rectal gland of Squalus acanthias. Stimulation by veratrine was prevented by the nerve channel blockers tetrodotoxin and procaine and was not evident in a preparation of dispersed rectal gland cells. Vasoactive intestinal peptide (VIP)-like immunoreactivity was detected by histological techniques in neuronal tissue within the rectal gland. Veratrine stimulation caused the release of immunoreactive VIP into the venous effluent of perfused glands. The stimulatory action of veratrine was inhibited by somatostatin, another neuropeptide known to be present in nerves of Squalus rectal gland. These findings suggest the likelihood of neural modulation of rectal gland function.

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Sodium Chloride Secretion in Rectal Gland of Dogfish, Squalus acanthias

Physiology ◽

10.1152/physiologyonline.1986.1.4.134 ◽

1986 ◽

Vol 1 (4) ◽

pp. 134-136

Author(s):

R. Greger ◽

E. Schlatter ◽

H. Gögelein

Keyword(s):

Sodium Chloride ◽

Basic Principle ◽

Peptide Hormones ◽

Chloride Secretion ◽

Hormonal Control ◽

Squalus Acanthias ◽

Rectal Gland

The rectal gland of the dogfish is specialized for the secretion of sodium chloride. The secretion is controlled by peptide hormones such as, for example, vasointestinal peptide. The mechanism of sodium chloride secretion is apparently similar to that present in mammalian epithelia such as the colon and trachea. This essay discusses the basic principle of sodium chloride secretion in the rectal gland and the mechanism of its hormonal control.

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Immunocytochemical studies of the Na-K-Cl cotransporter of shark kidney

AJP Renal Physiology ◽

10.1152/ajprenal.1996.270.6.f927 ◽

1996 ◽

Vol 270 (6) ◽

pp. F927-F936 ◽

Cited By ~ 4

Author(s):

D. Biemesderfer ◽

J. A. Payne ◽

C. Y. Lytle ◽

B. Forbush

Keyword(s):

Plasma Membrane ◽

Immunoelectron Microscopy ◽

Basolateral Membrane ◽

Distal Tubule ◽

Rectal Gland ◽

Apical Plasma Membrane ◽

Secretory Cells ◽

Weak Staining ◽

Basolateral Plasma Membrane ◽

Kidney Functions

The Na-K-Cl cotransporter (NKCC or BSC) has been described in numerous secretory and reabsorptive epithelia and is an important part of the mechanism of NaCl reabsorption in both the mammalian and elasmobranch kidneys. We have recently developed a panel of four monoclonal antibodies (MAbs) raised to the 195-kDa Na-K-Cl cotransport protein of the shark rectal gland (sNKCC1), which is expressed along the basolateral plasma membrane of secretory cells in this tissue (29). Here, we report immunologic studies of the Na-K-Cl cotransporter in the kidney of the dogfish shark Squalus acanthias. Western blot analysis of shark renal microsomes using MAbs J3, J7, and J25 identified proteins of approximately 195 and 150 kDa, whereas MAb J4 was not reactive. To define the cellular and subcellular distribution of the cotransport protein, immunofluorescence and immunoelectron microscopy studies were performed on fixed kidneys. Immunofluorescence microscopy on semithin (0.5-micron) cryosections demonstrated that MAbs J3, J7, and J25 intensely stained the apical plasma membrane of all distal tubule segments. Weak staining was also seen along the basolateral membrane of most distal nephrons. Immunoelectron microscopy confirmed this observation and showed that some of these segments were morphologically similar to diluting segments from other species. MAbs also reacted with the brush border and, to a lesser extent, the basolateral membrane of proximal tubules. This study supports the hypothesis that the lateral bundle zone of the elasmobranch kidney functions as a countercurrent exchanger and is consistent with the presence of multiple isoforms of the Na-K-Cl cotransporter in the shark kidney.

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Selective permeability barrier to urea in shark rectal gland

AJP Renal Physiology ◽

10.1152/ajprenal.00456.2004 ◽

2005 ◽

Vol 289 (1) ◽

pp. F83-F89 ◽

Cited By ~ 10

Author(s):

Joshua D. Zeidel ◽

John C. Mathai ◽

John D. Campbell ◽

Wily G. Ruiz ◽

Gerard L. Apodaca ◽

...

Keyword(s):

Activation Energy ◽

Epithelial Cells ◽

Water Flow ◽

Water Permeability ◽

Apical Membrane ◽

Basolateral Membrane ◽

Water Flux ◽

Rectal Gland ◽

Basolateral Membranes ◽

Urea Permeability

Elasmobranchs such as the dogfish shark Squalus acanthius achieve osmotic homeostasis by maintaining urea concentrations in the 300- to 400-mM range, thus offsetting to some degree ambient marine osmolalities of 900–1,000 mosmol/kgH2O. These creatures also maintain salt balance without losing urea by secreting a NaCl-rich (500 mM) and urea-poor (18 mM) fluid from the rectal gland that is isotonic with the plasma. The composition of the rectal gland fluid suggests that its epithelial cells are permeable to water and not to urea. Because previous work showed that lipid bilayers that permit water flux do not block flux of urea, we reasoned that the plasma membranes of rectal gland epithelial cells must either have aquaporin water channels or must have some selective barrier to urea flux. We therefore isolated apical and basolateral membranes from shark rectal glands and determined their permeabilities to water and urea. Apical membrane fractions were markedly enriched for Na-K-2Cl cotransporter, whereas basolateral membrane fractions were enriched for Na-K-ATPase. Basolateral membrane osmotic water permeability (Pf) averaged 4.3 ± 1.3 × 10−3 cm/s, whereas urea permeability averaged 4.2 ± 0.8 × 10−7 cm/s. The activation energy for water flow averaged 16.4 kcal/mol. Apical membrane Pf averaged 7.5 ± 1.6 × 10−4 cm/s, and urea permeability averaged 2.2 ± 0.4 × 10−7 cm/s, with an average activation energy for water flow of 18.6 kcal/mol. The relatively low water permeabilities and high activation energies argue strongly against water flux via aquaporins. Comparison of membrane water and urea permeabilities with those of artificial liposomes and other isolated biological membranes indicates that the basolateral membrane urea permeability is fivefold lower than would be anticipated for its water permeability. These results indicate that the rectal gland maintains a selective barrier to urea in its basolateral membranes.

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