Calcium and ATP regulation of ion transport in larval frog skin

2-methyl-9 α-fluorohydrocortisone and hydrocortisone sodium succinate increase both the rate and duration and, therefore, total quantity of ion transported in the isolated short-circuited frog skin measured over a 24-hour period. The ion transport is directly related to the bioelectric current generated, and based on Ussing's work, is assumed identical to the net flux of sodium ion. These steroids may make available transport energy that is not available to the untreated half of the skin by rerouting enzymatic pathways or by lowering the resistance of the membrane to ion transport and thereby more efficiently utilizing the energy available for transport.

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Pyrethroid stimulation of ion transport across frog skin

Environmental Toxicology and Chemistry ◽

10.1002/etc.5620220620 ◽

2003 ◽

Vol 22 (6) ◽

pp. 1330-1334 ◽

Cited By ~ 5

Author(s):

Giuseppe Cassano ◽

Vito Bellantuono ◽

Concetta Ardizzone ◽

Claudio Lippe

Keyword(s):

Ion Transport ◽

Frog Skin ◽

Stimulation Of

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EFFECTS OF METABOLIC INHIBITORS AND DRUGS ON ION TRANSPORT AND OXYGEN CONSUMPTION IN ISOLATED FROG SKIN

The Journal of General Physiology ◽

10.1085/jgp.41.2.397 ◽

1957 ◽

Vol 41 (2) ◽

pp. 397-417 ◽

Cited By ~ 49

Author(s):

Ernst G. Huf ◽

Norma S. Doss ◽

Joyce P. Wills

Keyword(s):

Ion Transport ◽

Frog Skin ◽

Ionic Composition ◽

Diethyl Malonate ◽

Metabolic Inhibitors ◽

Chemical Agent ◽

O2 Consumption ◽

Nacl Transport ◽

Exchange Adsorption ◽

Active Ion Transport

Active ion (NaCl) transport across isolated frog skin is discussed in relation to sodium and potassium composition and to O2 consumption of skin. A distinction is made between processes in skin related to "unidirectional active ion transport" and processes related to "maintenance electrolyte equilibrium;" i.e., ionic composition of skin. Several metabolic inhibitors were found that could be used in separating maintenance electrolyte equilibrium from unidirectional active ion transport. Fluoroacetate (up to 1 x 10–2M/liter) did not affect maintenance electrolyte equilibrium, but severely diminished the rate of active ion transport. This could also be accomplished with azide and diethyl malonate when 1 x 10–3 molar concentrations were used. When applied in higher concentrations, these two inhibitors, and several others, diminished active ion transport, but this was associated with changes in maintenance electrolyte equilibrium (gain of Na+ by and loss of K+ from skin). Similar observations were made when skins were subjected to K+-deficient media. Mersalyl and theophylline, in low concentrations, stimulated active ion transport without leading to changes in maintenance electrolyte equilibrium. Inhibition of active ion transport was found accompanied by decrease, increase, and unaltered over-all O2 consumption, depending on the kind of chemical agent used. A provisional scheme of the mechanism of unidirectional active ion transport is proposed. It is conceived as a process of metabolically supported ion exchange adsorption, involving a carrier, forming complexes with K+ and Na+, a trigger, K+ ions, and two spatially separated metabolic pathways.

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Effects of tumor promoters on sodium ion transport across frog skin

AJP Cell Physiology ◽

10.1152/ajpcell.1985.248.5.c457 ◽

1985 ◽

Vol 248 (5) ◽

pp. C457-C465 ◽

Cited By ~ 50

Author(s):

M. M. Civan ◽

D. Rubenstein ◽

T. Mauro ◽

T. G. O'Brien

Keyword(s):

Ion Transport ◽

Frog Skin ◽

Phorbol Esters ◽

Short Circuit ◽

Short Circuit Current ◽

Tumor Promoter ◽

Tumor Promoters ◽

Transport Effects ◽

Preliminary Study ◽

Stimulation Of

Phorbol esters are tumor promoters and mitogens whose effects may be mediated by changes in ion transport across membranes. Clarification of the transport effects of these agents should be facilitated by using a well-characterized model epithelial system whose intracellular and transmural parameters are readily measurable. The current results constitute a preliminary study of the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), phorbol-12,13-dibutyrate (PDBU), and phorbol on the short-circuit current (Isc) across frog skin. TPA produced two effects: a stimulation of Isc of variable magnitude and a far more constant inhibition of the natriferic action of vasopressin. These effects appear related to the action of TPA as a tumor promoter insofar as PDBU (an active ester) also inhibited the natriferic response to vasopressin, whereas phorbol (inactive as a tumor promoter) had no significant effect. TPA is largely active from the mucosal medium, inhibits the natriferic response to adenosine 3',5'-cyclic monophosphate (cAMP) as well as that to vasopressin, and does not stimulate Isc in the presence of 10(-4) M mucosal amiloride. Inhibition of prostaglandin E1 production by indomethacin had no effect on the actions of TPA. The results indicate that frog skin is a promising model for studying the transport effects of the phorbol esters. The data further suggest that TPA acts on frog skin by activating the physiological amiloride- and cAMP-sensitive channels gating apical Na+ entry from the mucosal medium into the epithelial cells.

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