pCMBS-induced swelling of dogfish (Squalus acanthias) rectal gland cells: role of the Na+,K+-ATPase and the cytoskeleton

1990 ◽  
Vol 1025 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Arnost Kleinzeller ◽  
George W. Booz ◽  
John W. Mills ◽  
Fuad N. Ziyadeh
Keyword(s):  
Squalus Acanthias ◽  
Rectal Gland ◽  
Gland Cells

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.

Mode of action of somatostatin to inhibit secretion by shark rectal gland

1985 ◽  
Vol 249 (3) ◽  
pp. R329-R334 ◽  
Author(s):  
P. Silva ◽  
J. S. Stoff ◽  
D. R. Leone ◽  
F. H. Epstein
Keyword(s):  
Cellular Response ◽  
Specific Binding ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Squalus Acanthias ◽  
Rectal Gland ◽  
Gland Cells ◽  
Mechanism Of Inhibition ◽  
Rectal Glands ◽  
Stimulation Of

The rectal gland of the spiny dogfish Squalus acanthias is stimulated to secrete chloride by vasoactive intestinal peptide (VIP) in a way that is inhibited by somatostatin. The mechanism of inhibition by somatostatin was studied in isolated perfused rectal glands and separated rectal gland cells. Somatostatin did not alter the specific binding of VIP to rectal gland cells but inhibited their accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) in response to VIP. In isolated perfused glands, somatostatin inhibited the stimulation of secretion produced by VIP, adenosine, and forskolin, as well as by dibutyryl cAMP plus a phosphodiesterase inhibitor. The results support the hypothesis of both a proximal and a distal locus, in the cascade of events leading from adenylate cyclase activation to cellular response, at which somatostatin exerts an inhibitory effect.

scholarly journals Sugar uptake, metabolism, and chloride secretion in the rectal gland of the spiny dogfish Squalus acanthias

2020 ◽  
Vol 319 (1) ◽  
pp. R96-R105
Author(s):  
Rolf Kinne ◽  
Katherine C. Spokes ◽  
Patricio Silva
Keyword(s):  
Glycogen Phosphorylase ◽  
Chloride Secretion ◽  
Squalus Acanthias ◽  
Rectal Gland ◽  
Sugar Uptake ◽  
Spiny Dogfish ◽  
Gland Cells ◽  
Exogenous Glucose ◽  
Glucose Transporter 2 ◽  
Rectal Glands

The rectal gland of the spiny dogfish Squalus acanthias secretes a salt solution isosmotic with plasma that maintains the salt homeostasis of the fish. It secretes salt against an electrochemical gradient that requires the expenditure of energy. Isolated rectal glands perfused without glucose secrete salt, albeit at a rate about 30% of glands perfused with 5 mM glucose. Gradually reducing the glucose concentration is associated with a progressive decrease in the secretion of chloride. The apparent Km for the exogenous glucose-dependent chloride secretion is around 2 mM. Phloretin and cytochalasin B, agents that inhibit facilitated glucose carriers of the solute carrier 2 (Slc2) family such as glucose transporter 2 (GLUT2), do not inhibit the secretion of chloride by the perfused rectal glands. Phloridzin, which inhibits Slc5 family of glucose symporters, or α-methyl-d-glucoside, which competitively inhibits the uptake of glucose through Slc5 symporters, inhibit the secretion of chloride. Thus the movement of glucose into the rectal gland cells appears to be mediated by a sodium-glucose symporter. Sodium-glucose cotransporter 1 (SGLT1), the first member of the Slc5 family of sodium-linked glucose symporters, was cloned from the rectal gland. No evidence of GLUT2 was found. The persistence of secretion of chloride in the absence of glucose in the perfusate suggests that there is an additional source of energy within the cells. The use of 2-mercapto-acetate did not result in any change in the secretion of chloride, suggesting that the oxidation of fatty acids is not the source of energy for the secretion of chloride. Perfusion of isolated glands with KCN in the absence of glucose further reduces the secretion of chloride but does not abolish it, again suggesting that there is another source of energy within the cells. Glucose was measured in the rectal gland cells and found to be at concentrations in the range of that in the perfusate. Glycogen measurements indicated that there are significant stores of glucose in the rectal gland. Moreover, glycogen synthase was partially cloned from rectal gland cells. The open reading frame of glycogen phosphorylase was also cloned from rectal gland cells. Measurements of glycogen phosphorylase showed that the enzyme is mostly in its active form in the cells. The cells of the rectal gland of the spiny dogfish require exogenous glucose to fully support the active secretion of salt. They have the means to transport glucose into the cells in the form of SGLT1. The cells also have an endogenous supply of glucose as glycogen and have the necessary elements to synthesize, store, and hydrolyze it.

Osmoregulation by the Prenatal Spiny Dogfish, Squalus Acanthias

1982 ◽  
Vol 101 (1) ◽  
pp. 295-305 ◽  
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:

Neural control of shark rectal gland

1988 ◽  
Vol 255 (2) ◽  
pp. R212-R216 ◽  
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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