Cyclic AMP stimulates ouabain-insensitive ion movement in shark rectal gland

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.

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Cadmium disrupts the signal transduction pathway of both inhibitory and stimulatory receptors regulating chloride secretion in the shark rectal gland

Journal of Experimental Zoology ◽

10.1002/(sici)1097-010x(19971201)279:5<530::aid-jez17>3.0.co;2-b ◽

1997 ◽

Vol 279 (5) ◽

pp. 530-536 ◽

Cited By ~ 8

Author(s):

John N. Forrest ◽

Stephen G. Aller ◽

Stephen J. Wood ◽

Martha A. Ratner ◽

John K. Forrest ◽

...

Keyword(s):

Signal Transduction ◽

Signal Transduction Pathway ◽

Chloride Secretion ◽

Rectal Gland ◽

Transduction Pathway ◽

Shark Rectal Gland

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

AJP Cell Physiology ◽

10.1152/ajpcell.1991.260.4.c824 ◽

1991 ◽

Vol 260 (4) ◽

pp. C824-C831 ◽

Cited By ~ 31

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.

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

AJP Cell Physiology ◽

10.1152/ajpcell.1989.257.2.c377 ◽

1989 ◽

Vol 257 (2) ◽

pp. C377-C384 ◽

Cited By ~ 23

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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