Nerve Stimulation and Electrical Properties of Frog Skin

The suitability of frog skin glands as a model for the study of secretory mechanisms in exocrine glands was explored. Periodic voltage clamp was used to determine continually the short-circuit current, chord conductance, and electromotive force of frog skin during neural and pharmacological activation of the skin glands. Both the chord conductance and the short-circuit current increased with glandular activation; the temporal dissociation of these increases suggests that there are at least two separate components to the secretory response. The sensitivity of the secretory electrical changes to changes in the ionic composition of the bathing solutions supports the notion of electrogenic chloride active transport as being basic to the activity of the exocrine glands.

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Chloride transport in glands of frog skin

AJP Cell Physiology ◽

10.1152/ajpcell.1983.244.3.c221 ◽

1983 ◽

Vol 244 (3) ◽

pp. C221-C226 ◽

Cited By ~ 25

Author(s):

I. G. Thompson ◽

J. W. Mills

Keyword(s):

Frog Skin ◽

Chloride Transport ◽

Short Circuit ◽

Short Circuit Current ◽

Serosal Side ◽

Adrenergic Stimulation ◽

Beta Adrenergic ◽

Skin Glands ◽

Frog Skin Glands ◽

Beta Adrenergic Agonist

The effects of beta-adrenergic stimulation on the bidirectional fluxes of Na+ and Cl- across the frog skin glands were determined. Isoproterenol elicited net serosal-to-mucosal fluxes of both Na+ (JNanet) and Cl- (JClnet) equal to 0.19 +/- 0.05 (SE) and 0.57 +/- 0.05 mueq X cm-2 X h-1, respectively. The residual current (JClnet - JNanet) of 0.38 +/- 0.05 mueq X cm-2 X h-1 closely approximates the isoproterenol-induced short-circuit current of 0.30 +/- 0.04 mueq X cm-2 X h-1. Furosemide added to the serosal side prior to isoproterenol inhibited the isoproterenol-induced net fluxes of both Na+ and Cl-. The addition of dibutyryl cAMP and 3-isobutyl-1-methylxanthine to the serosal side mimicked the action of isoproterenol by stimulating glandular short-circuit current. We conclude that an active Cl(-)-transport mechanism resides in the frog skin glands and is 1) stimulated by a beta-adrenergic agonist (its action is mimicked by cAMP) and 2) inhibited by the loop diuretic furosemide.

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Relationships between calcium and chloride transport in frog skin glands

AJP Renal Physiology ◽

10.1152/ajprenal.1986.251.4.f647 ◽

1986 ◽

Vol 251 (4) ◽

pp. F647-F654 ◽

Cited By ~ 1

Author(s):

F. N. Ziyadeh ◽

E. Kelepouris ◽

Z. S. Agus

Keyword(s):

Frog Skin ◽

Chloride Transport ◽

Short Circuit ◽

Calcium Ionophore ◽

Ionophore A23187 ◽

Bathing Medium ◽

Beta Adrenergic ◽

Cl Secretion ◽

Skin Glands ◽

Frog Skin Glands

Frog skin gland, a furosemide-sensitive Cl(-)-secreting epithelium, exhibits Cl(-)-dependent Ca2+ secretion in response to stimulation by beta-adrenergic agonists. In this study, we further explored the relationships between Cl- and Ca2+ secretion in frog skin using 45Ca fluxes and short-circulating technique. On addition of isoproterenol (ISO) or 8-(p-chlorophenylthio)-cAMP, a significant positive correlation was demonstrated between Ca2+ secretion and Cl- secretion. Because Cl- transport in other Cl(-)-transporting epithelia may be modulated by prostaglandins or by changes in cytosolic Ca2+ activity, in addition to modulation by cAMP, we also examined the effects of prostaglandins (PG)E2 and F2 alpha, indomethacin (INDO), and the calcium ionophore A23187. Treatment with PGE2, PGF2 alpha, or A23187 at a dose of 10(-5) M resulted in marked stimulation in the amiloride-resistant short-circuit current, a reflection of Cl- secretion. This current was inhibited by furosemide addition or removal of Cl- from the bathing medium. However, and in contrast to stimulation with ISO or cAMP, PGE2, PGF2 alpha, and A23187 failed to induce Ca2+ secretion. In addition, the stimulation of Cl- secretion by A23187 was abolished by INDO (10(-6) M) pretreatment. Thus frog skin glands secrete Cl- via two mechanisms: one mediated by beta-adrenergic-cAMP stimulation and the other by activation of prostaglandin metabolism induced by changes in cytosolic Ca2+. Only the former pathway is associated with Ca2+ secretion. Furthermore, to account for the Cl- dependence of Ca2+ secretion, we postulate the existence of a Ca2+-Cl- cotransport system stimulated by cAMP.

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Photocurrent density and electrical properties of Bi0.5Na0.5TiO3-BaNi0.5Nb0.5O3 ceramics

Journal of Advanced Ceramics ◽

10.1007/s40145-021-0497-7 ◽

2021 ◽

Author(s):

Mingqiang Zhong ◽

Qin Feng ◽

Changlai Yuan ◽

Xiao Liu ◽

Baohua Zhu ◽

...

Keyword(s):

Electrical Properties ◽

Photovoltaic Effect ◽

Short Circuit ◽

Short Circuit Current ◽

Photocurrent Density ◽

Open Circuit ◽

Light Conditions ◽

X Ray Diffraction ◽

Solid State Method ◽

X Ray

AbstractIn this work, the (1−x)Bi0.5Na0.5TiO3-xBaNi0.5Nb0.5O3 (BNT-BNN; 0.00 ⩽ x ⩽ 0.20) ceramics were prepared via a high-temperature solid-state method. The crystalline structures, photovoltaic effect, and electrical properties of the ceramics were investigated. According to X-ray diffraction, the system shows a single perovskite structure. The samples show the normal ferroelectric loops. With the increase of BNN content, the remnant polarization (Pr) and coercive field (Ec) decrease gradually. The optical band gap of the samples narrows from 3.10 to 2.27 eV. The conductive species of grains and grain boundaries in the ceramics are ascribed to the double ionized oxygen vacancies. The open-circuit voltage (Voc) of ∼15.7 V and short-circuit current (Jsc) of ∼1450 nA/cm2 are obtained in the 0.95BNT-0.05BNN ceramic under 1 sun illumination (AM1.5G, 100 mW/cm2). A larger Voc of 23 V and a higher Jsc of 5500 nA/cm2 are achieved at the poling field of 60 kV/cm under the same light conditions. The study shows this system has great application prospects in the photovoltaic field.

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Transepithelial transport kinetics and Na entry in frog skin: effects of novobiocin

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.6.1866 ◽

1976 ◽

Vol 231 (6) ◽

pp. 1866-1874 ◽

Cited By ~ 13

Author(s):

LJ Cruz ◽

TU Biber

Keyword(s):

Kinetic Parameters ◽

Frog Skin ◽

Short Circuit ◽

Short Circuit Current ◽

Close Correlation ◽

Transport Kinetics ◽

Transepithelial Transport ◽

Linear Component ◽

Na Transport ◽

Transepithelial Na Transport

Na+ entry across the outer surface of frog skin and transepithelial Na transport were studied simultaneously at different [Na] in either the presence or absence of novobiocin by direct measurements of J12 (unidirectional uptake) and Io (short-circuit current). J12 consisted of two components: one linear, the other saturable. The kinetic parameters of the saturating components in controls were close to the kinetic parameters of overall transepithelial transport (Jm12 = 1.68+/-0.13 mleq cm-2h-1; Io =1.80+/-0.14 mueq cm-2h-1. K12 = 6.02+/-1.27 mM;Kio=6.12+/-1.33 mM). Novobiocin significantly augmented net transepithelial Na transport by increasing J13. J31 remained unaffected. A 1:1 relationship between the saturating component of J12 and Io was observed in both treated and untreated skins at all [Na] tested. (Jm12Iom, k12, and Kio were significantly larger in treated skins, but despite very drastic changes in transport rates, a close correlation between kinetic parameters of entry step and transepithelial transport was maintained. This suggests that the kinetics of transepithelial transport may simply reflect those of the rate-limiting step: the Na entry across the outer barrier of the skin. The results indicate that the linear component of J12 is not involved in transepithelial transport kinetics.

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Effects of choline and other quaternary ammonium compounds on Na movements in frog skin

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1963.205.5.1063 ◽

1963 ◽

Vol 205 (5) ◽

pp. 1063-1066 ◽

Cited By ~ 12

Author(s):

Robert I. Macey ◽

Daniel C. Koblick

Keyword(s):

Quaternary Ammonium ◽

Frog Skin ◽

Short Circuit ◽

Short Circuit Current ◽

Quaternary Ammonium Compounds ◽

Average Increase ◽

Current Increase ◽

Sodium Flux ◽

Radioactive Sodium ◽

Ammonium Compounds

Effects of choline on short-circuit current and radioactive sodium flux were measured in isolated frog skins. Replacement of control ions (K or Mg) by choline in the outside solution increased the short-circuit current and inward Na flux. When K was the control ion, the average increase in short-circuit current was 52%; with Mg, it was 36%. In both cases, the increase in inward Na flux accounted for about 75% of the short-circuit current increase, while passive choline movement possibly accounted for the remainder. Similar results were obtained using tetramethylammonium and tetraethylammonium in place of choline. One implication of these results is that studies in which choline is used as an inert substitute for Na must be interpreted with caution.

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Effect of calcium on ion transport and electrical properties of tracheal epithelium

Journal of Applied Physiology ◽

10.1152/jappl.1978.44.6.900 ◽

1978 ◽

Vol 44 (6) ◽

pp. 900-904 ◽

Cited By ~ 11

Author(s):

M. G. Marin ◽

M. M. Zaremba

Keyword(s):

Electrical Properties ◽

Ion Transport ◽

Calcium Concentration ◽

Short Circuit ◽

Electrical Potential ◽

Short Circuit Current ◽

Tracheal Epithelium ◽

Electrical Potential Difference ◽

Tracheal Lumen

Active transport of Cl- toward the tracheal lumen and Na+ away from the lumen creates an electrical potential difference across dog tracheal epithelium. This study examined in vitro the effect of varying calcium concentration in the bathing media on the ion transport and electrical properties of dog tracheal epithelium. In six pairs of epithelia, changing calcium concentration from 1.9 to 0 mM resulted in a significant decrease in electrical resistance, from 318 +/- 36 to 214 +/- 24 omega.cm2. Short-circuit current and net Cl- and Na+ fluxes measured under short-circuit conditions were not changed significantly. Changing calcium concentration from 1.9 to 10 mM resulted in no significant change from control in the electrical properties nor in net Cl- and Na+ fluxes (short-circuit conditions). Histamine (10(-4) M) produced a significantly smaller increase in short-circuit current in 0 than in 1.9 mM Ca2+ (+5 +/- 2 vs. +12 +/- 2 microamperemeter/cm2). However, electrical changes were not significantly different in 1 or 10 mM Ca2+. These results indicate that calcium lack increased permeability of tracheal epithelium and that the increase in short-circuit current due to histamine depended in part on calcium.

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Effect of amiloride and some of its analogues of cation transport in isolated frog skin and thin lipid membranes.

The Journal of General Physiology ◽

10.1085/jgp.68.1.43 ◽

1976 ◽

Vol 68 (1) ◽

pp. 43-63 ◽

Cited By ~ 70

Author(s):

D J Benos ◽

S A Simon ◽

L J Mandel ◽

P M Cala

Keyword(s):

Lipid Membranes ◽

Frog Skin ◽

Short Circuit ◽

Short Circuit Current ◽

Active Species ◽

Biologically Active ◽

Lipid Bilayer Membranes ◽

Inhibitory Interaction ◽

Charged Form ◽

Transport Site

The inhibition of short-circuit current (Isc) in isolated frog skin and the induction of surface potentials in lipid bilayer membranes produced by the diuretic drug amiloride and a number of its chemical analogues was studied. The major conclusions of our study are: (a) The charged form of amiloride is the biologically active species. (b) Both the magnitude of Isc and the amiloride inhibitory effect are sensitive to the ionic milieu bathing the isolated skin, and these two features are modulated at separate and distinct regions on the transport site. (c) Amiloride is very specific in its inhibitory interaction with the Na+ transport site since slight structural modifications can result in significant changes in drug effectiveness. We found that substitutions at pyrazine ring position 5 greatly diminish drug activity, while changes at position 6 are less drastic. Alterations in the guanidinium moiety only diminish activity if the result is a change in the spatial orientation of the amino group carrying the positive charge. (d) Amiloride can bind to and alter the charge on membrane surfaces, but this action cannot explain its highly specific effects in biological systems.

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Calcium channel blockers inhibit amiloride-stimulated short-circuit current in frog tadpole skin

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1992.263.4.r827 ◽

1992 ◽

Vol 263 (4) ◽

pp. R827-R833 ◽

Cited By ~ 1

Author(s):

T. C. Cox

Keyword(s):

Calcium Channel ◽

Calcium Channel Blockers ◽

Time Course ◽

Frog Skin ◽

Short Circuit ◽

Short Circuit Current ◽

Cation Channels ◽

Channel Blockers ◽

Ussing Chambers ◽

Frog Tadpole

The larval frog skin has a very high electrical resistance and a corresponding low rate of transepithelial ion transport. Amiloride, a blocker of sodium transport in adult skin, transiently stimulates rather than inhibits short-circuit current (Isc) across larval skin. The time course and concentration response to amiloride and the effects of calcium channel blockers on Isc were studied with larval frog skin mounted in modified Ussing chambers. The amiloride (1 mM) transient was markedly blunted if the skin was previously exposed to low amiloride (0.01-0.1 mM) concentrations. The calcium channel blockers verapamil, nitrendipine, diltiazem, W-7, and lanthanum all blocked the amiloride transient. Diltiazem itself caused a rapid transient in Isc, indicating that it may be a partial agonist. These data suggest that the amiloride-stimulated cation channels rapidly desensitize in a manner similar to the acetylcholine receptor. The decline in Isc after amiloride stimulation could be caused by amiloride block of the open channel. Blockade of amiloride stimulation by well-known calcium channel blockers suggests that these larval cation channels may have some characteristics in common with calcium channels.

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