cAMP Increases the Apical Cl- Conductance in the Rectal Gland of Squalus acanthias

1987 ◽  
pp. 9-13
Author(s):  
R. Greger ◽  
E. Schlatter
Keyword(s):  
Squalus Acanthias ◽  
Rectal Gland ◽  
Cl Conductance

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

1987 ◽  
Vol 409 (1-2) ◽  
pp. 100-106 ◽  
Author(s):  
Rainer Greger ◽  
Heinz Gögelein ◽  
Eberhard Schlatter
Keyword(s):  
Potassium Channels ◽  
Basolateral Membrane ◽  
Squalus Acanthias ◽  
Rectal Gland

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.

cAMP-activated C1 conductance is expressed in Xenopus oocytes by injection of shark rectal gland mRNA

1991 ◽  
Vol 260 (3) ◽  
pp. C664-C669 ◽  
Author(s):  
S. K. Sullivan ◽  
K. Swamy ◽  
M. Field
Keyword(s):  
Xenopus Oocytes ◽  
Functional Characterization ◽  
Equilibrium Potential ◽  
Rectal Gland ◽  
Calcium Buffer ◽  
Cl Channel ◽  
Shark Rectal Gland ◽  
Cl Channels ◽  
Cl Conductance

Development of reliable expression systems for use in identification and functional characterization of proteins required for secretory Cl channel activity is key to understanding the molecular basis of cystic fibrosis (CF). Until now, heterologous expression of epithelial Cl channels had not been accomplished. We show here that Xenopus oocytes express an adenosine 3',5'-cyclic monophosphate (cAMP)-activated Cl conductance after injection of mRNA from shark rectal gland. Current through this conductance was rapidly activated by intracellular application of cAMP, reversed near the chloride equilibrium potential (ECl), blocked by the Cl channel inhibitor 5-nitro-2-(3-phenylpropylamino) benzoate, and was not affected by preincubation with the intracellular calcium buffer bis-(2-amino-5-methylphenoxy)-ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester, a condition that prohibits activation of the endogenous Ca-activated Cl conductance.

Sodium Chloride Secretion in Rectal Gland of Dogfish, Squalus acanthias

Physiology ◽  
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.

Cl- secretion by cultured shark rectal gland cells. II. Effects of forskolin on cellular electrophysiology

1991 ◽  
Vol 260 (4) ◽  
pp. C824-C831 ◽  
Author(s):  
W. M. Moran ◽  
J. D. Valentich
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Ringer Solution ◽  
Rectal Gland ◽  
Electrical Potential Difference ◽  
Electrophysiological Properties ◽  
Shark Rectal Gland ◽  
Membrane Electrical Potential ◽  
Cl Conductance

Employing microelectrode techniques we have assessed the cellular electrophysiological properties of shark rectal gland (SRG) cells in primary culture. In the absence of secretagogues a 10-fold reduction in the Cl- concentration of the apical superfusate shark Ringer solution had little effect on either apical membrane electrical potential difference (Va) or fractional resistance (fRa), indicating little, if any, apical membrane Cl- conductance. Superfusing the basolateral surface with high-K+ shark Ringer solution (K+ increased 10-fold) depolarized the basolateral membrane electrical potential difference (Vb) by 43 mV, indicating that this barrier is largely K+ conductive. In addition, basolateral Ba2+ (5 mM) depolarized Vb by 12 mV and reduced fRa from 0.92 to 0.58, results consistent with a K(+)-conductive basolateral membrane in unstimulated SRG cells. Basolateral forskolin (10(-6) M) depolarized Va by 25 mV and caused a dramatic reduction in fRa from 0.97 to approximately 0.10. Under these conditions, a 10-fold decrease in apical superfusate Cl- concentration depolarized Va by 37 mV, revealing an adenosine 3',5'-cyclic monophosphate-induced apical membrane Cl- conductance. The time course of the forskolin-induced changes in Va and Vb suggests that the basolateral membrane K+ conductance increased and maintained the driving force for apical Cl- exit, as in other Cl(-)-secreting epithelia. These electrophysiological properties compare favorably with those of the perfused SRG tubule and indicate that SRG primary cultures are a suitable model for Cl(-)-secreting epithelia.

Propionate induces cell swelling and K+ accumulation in shark rectal gland

1989 ◽  
Vol 257 (2) ◽  
pp. C377-C384 ◽  
Author(s):  
G. M. Feldman ◽  
F. N. Ziyadeh ◽  
J. W. Mills ◽  
G. W. Booz ◽  
A. Kleinzeller
Keyword(s):  
Atpase Activity ◽  
Propionic Acid ◽  
Exchange Process ◽  
Squalus Acanthias ◽  
Cell Swelling ◽  
Rectal Gland ◽  
Structural Elements ◽  
Acid Diffusion ◽  
Shark Rectal Gland ◽  
Solute Accumulation

Small organic anions have been reported to induce cell solute accumulation and swelling. To investigate the mechanism of swelling, we utilized preparations of rectal gland cells from Squalus acanthias incubated in medium containing propionate. Propionate causes cells to swell by diffusing across membranes in its nonionic form, acidifying cell contents, and activating the Na+-H+ antiporter. The Na+-H+ exchange process tends to correct intracellular pH (pHi), and thus it maintains a favorable gradient for propionic acid diffusion and allows propionate to accumulate. Activation of the Na+-H+ antiport also facilitates Na+ entry into the cell and Nai accumulation. At the same time Na+-K+-ATPase activity, unaffected by propionate, replaces Nai with Ki, whereas the K+ leak rate, decreased by propionate, allows Ki to accumulate. As judged by 86Rb+ efflux, the reduction in K+ leak was not due to propionate-induced cell acidification or reduction in Cli concentration. Despite inducing cell swelling, propionate did not disrupt cell structural elements and F actin distribution along cell membranes.

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