Hydrosmotic salt effect in toad skin: Urea permeability and glutaraldehyde fixation of water channels

Aboulafia, Jeannine; Lacaz-Vieira, Francisco

doi:10.1007/bf01871225

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…The greater in vitro water efflux (especially in infected animals) may be a consequence of solvent drag and differences in ionic gradient across the skin, where water is pulled paracellularly across the membrane against its concentration gradient due to coupling with the paracellular movement of solutes such as NaCl (25,75). Evidence for solvent-coupled water movement has been found in toad skin (1,5). Given that Bd-infected frogs lose large amounts of salt via leakage across the ventral skin surface (78), solute-linked water movement may explain why infected frogs also have greater rates of water efflux despite an osmotic gradient that should promote net water uptake.…”

Section: Bd Infection Impairs Cutaneous Water Uptake Rates But Not Tomentioning

confidence: 99%

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

McKercher

Cramp

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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Chytridiomycosis, a lethal skin disease caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd), disrupts skin function of amphibians, interfering with ionic and osmotic regulation. To regulate fungal loads, amphibians increase their rate of skin sloughing. However, sloughing also causes a temporary loss of ionic and osmotic homeostasis due to disruption of the skin, a key osmoregulatory organ. The combined effects of increased sloughing frequency and chytridiomycosis contribute to the high rates of mortality from Bd infections. However, the mechanisms responsible for the loss of cutaneous osmotic regulation remain unknown. We measured the changes in whole animal water uptake rates, in vitro transcutaneous water fluxes across the ventral skin, and the mRNA expression of epithelial water transport proteins (aquaporins, AQPs) and junctional proteins in Bd-infected and uninfected Litoria caerulea skin. We hypothesize that infected frogs would show reduction/inhibition in cutaneous water transporters responsible for regulating water balance, and sloughing would exacerbate cutaneous water fluxes. We found that infected, nonsloughing frogs had an impaired rate of water uptake and showed increased rates of in vitro water efflux across the ventral skin. In uninfected frogs, the expression of AQPs and junction genes increased significantly with sloughing, which may assist in regulating cutaneous water movements and barrier function in the newly exposed skin. In contrast, infected frogs did not show this postsloughing increase in AQP gene expression. The combination of increased sloughing frequency, impaired water uptake rates, and increased rates of water loss likely contributes to the loss of osmotic homeostasis in frogs infected with Bd.

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Section: Bd Infection Impairs Cutaneous Water Uptake Rates But Not Tomentioning

confidence: 99%

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

McKercher

Cramp

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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“…To distinguish between these possibilities we attempted to stabilize the water channels in the plasma membrane. When ADH-treated urinary bladders are briefly exposed to a weak solution of glutaraldehyde (0.1%), water flux becomes insensitive to inhibitors of cytoskeletal function, and the water permeation pathway is fixed in an open state (Eggena, 1983;Aboulafia and Lacaz-Vieira, 1985). This technique should allow distinction between a direct inhibition of JH~o at the level of the water channel and indirect effects via the cytoskeleton.…”

Section: Site Of Action Of H+-atpase Inhibitorsmentioning

confidence: 99%

Common channels for water and protons at apical and basolateral cell membranes of frog skin and urinary bladder epithelia. Effects of oxytocin, heavy metals, and inhibitors of H(+)-adenosine triphosphatase.

Harvey

Lacoste

Ehrenfeld

1991

The Journal of General Physiology

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We have compared the response of proton and water transport to oxytocin treatment in isolated frog skin and urinary bladder epithelia to provide further insights into the nature of water flow and H ÷ flux across individual apical and basolateral cell membrances. In isolated spontaneous sodium-transporting frog skin epithelia, lowering the pH of the apical solution from 7.4 to 6.4, 5.5, or 4.5 produced a fall in pH~ in principal cells which was completely blocked by amiloride (50 ~.M), indicating that apical Na ÷ channels are permeable to protons. When sodium transport was blocked by amiloride, the H ÷ permeability of the apical membranes of principal cells was negiligible but increased dramatically after treatment with antidiuretic hormone (ADH). In the latter condition, lowering the pH of the apical solution caused a voltage-dependent intracellular acidification, accompanied by membrane depolarization, and an increase in membrane conductance and transepithelial current. These effects were inhibited by adding Hg '÷ (100 o.M) or dicydohexylcarbodiimide (DCCD, to the apical bath. Net titratable H ÷ flux across frog skin was increased from 30 -+ 8 to 115 _ 18 neq-h-l-cm -~ (n = 8) after oxytocin treatment (at apical pH 5.5 and serosal pH 7.4) and was completely inhibited by DCCD (10 -5 M). The basolateral membranes of the principal cells in frog skin epithelium were found to be spontaneously permeable to H ÷ and passive electrogenic H ÷ transport across this membrane was not affected by oxytocin. Lowering the pH of the basolateral bathing solution (pHb) produced an intraceUular acidification and membrane depolarization (and an increase in conductance when the normal dominant K ÷ conductance of this membrane was abolished by Ba 2÷ 1 mM). These effects of low pH b were blocked by micromolar concentrations of heavy metals (Zn 2÷, Ni ~÷, Co 2÷, Cd ~+, and Hg~+). 750THE JOURNAL OF GENERAL PHYSIOLOGY • VOLUME 97. 1991 (50 mU/ml) produced a transepithelial current (3 p~A'cm -~ at pH b 5.5) which was blocked by 100 I~M of rig z+, Zn 2+, or Ni 2+ at the basolateral side, and by DCCD (10 -~' M) or Hg 2+ (100 p~M) from the apical side. The net hydroosmotic water flux (JH~o) induced by oxytocin in frog bladder sacs was blocked by inhibitors of H+-adenosine triphosphatase (ATPase). Diethylstilbestrol (DES 10 -5 M), oligomycin (10 -~ M), and DCCD (10 -~ M) preventedJH~o when present in the lumen. These effects cannot be attributed to inhibition of metabolism since cyanide (10 -4 M), or 2-deoxyglucose (10 -3 M) had no effect onJ~o. DCCD and oligomycin, which are known to interact with the F o proton channel of F~-F o H+-ATPase also appear to act directly on the apical water channel in glutaraldehyde-fixed bladders. The sulfhydryl group reagent n-ethylmaleimide (10 -4 M) which interacts with the F~-Fo-type H+-ATPase in renal epithelia as well as vacuolar H+-ATPase produced an 85% inibition of JH~o. Oxytocin failed to activate a net water flux when Zn 2÷ (100 ~M) or Hg z+ (100 ~M) were present in the serosal solution, ...

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“…In epithelial physiology, GA was used as a fixative (at concentrations higher than 2 % w/v) for preserving water and urea channels induced by antidiuretic MS 7928 5D. -G. AI4RGINYEANU A-ND W. VAN DRIESSCHE hormone in urinary bladders (Eggena, 1983), or by hypertonic outer solutions in the amphibian skin (Aboulafia & Lacaz-Vieira, 1985).…”

Section: Introductionmentioning

confidence: 99%

Effects of millimolar concentrations of glutaraldehyde on the electrical properties of frog skin.

Mǎrgineanu

Driessche

1990

The Journal of Physiology

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1. The effects of millimolar concentrations of glutaraldehyde on the electrophysiological properties of the epithelium of frog skin (Rana temporaria) were investigated. We recorded short-circuit current (Isc), transepithelial conductance (Gt) and impedance (Zt), fractional resistance (fRo) and the potential difference across the apical membrane (Vo). We used either Na+ or K+ as major mucosal cations to compare the effects on transepithelial Na+ and K+ currents (INa and IK) and thus on the apical Na+ and K+ permeabilities. 2. At concentrations above 0.005% (w/v) or 0.5 mM, glutaraldehyde irreversibly and completely inhibits both INa and IK within 2-3 h. The initial time courses of the inhibition of transepithelial currents following serosal and mucosal applications of the compound markedly differ. 3. Glutaraldehyde decreased Gt in sulphate Ringer solutions while it augmented Gt severalfold in chloride Ringer solution. 4. Measurements of the transepithelial impedance of tissues incubated with sulphate solutions showed that glutaraldehyde increased the resistances of both apical and basolateral membranes significantly. The capacitance of the apical membrane was augmented, while the basolateral membrane capacitance was drastically decreased. 5. Microelectrode impalements of the granulosum cells showed that glutaraldehyde decreased Vo by more than 40 mV and increased fRo, which reached values around 90%. 6. The role of free amino groups in ion-transporting proteins and the potential non-fixative uses of protein cross-linkers in epithelia are discussed.

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Hydrosmotic salt effect in toad skin: Urea permeability and glutaraldehyde fixation of water channels

Cited by 7 publications

References 20 publications

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

Common channels for water and protons at apical and basolateral cell membranes of frog skin and urinary bladder epithelia. Effects of oxytocin, heavy metals, and inhibitors of H(+)-adenosine triphosphatase.

Effects of millimolar concentrations of glutaraldehyde on the electrical properties of frog skin.

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