Effect of melittin on the apical membrane Na+ and C1- conductances of frog cornea epithelium

1997 ◽  
Vol 75 (3) ◽  
pp. 199-204 ◽  
Author(s):  
G Carrasquer ◽  
S Yang ◽  
M Schwartz ◽  
M A Dinno
Keyword(s):  
Apical Membrane ◽  
Cornea Epithelium ◽  
Frog Cornea

Effect of melittin on the apical membrane Na+ and C1- conductances of frog cornea epithelium

1997 ◽  
Vol 75 (3) ◽  
pp. 199-204
Author(s):  
G. Carrasquer ◽  
S. Yang ◽  
M. Schwartz ◽  
M.A. Dinno
Keyword(s):  
Apical Membrane ◽  
Cornea Epithelium ◽  
Frog Cornea

Electrogenicity of the Na-K-ATPase pump in bullfrog cornea epithelium

1985 ◽  
Vol 249 (2) ◽  
pp. F185-F191
Author(s):  
G. Carrasquer ◽  
S. Ahn ◽  
M. Schwartz ◽  
W. S. Rehm
Keyword(s):  
Aqueous Solution ◽  
Relative Resistance ◽  
Normal Response ◽  
Conductive Pathway ◽  
K Concentration ◽  
Cornea Epithelium ◽  
Frog Cornea

The effect of changing the K concentration in the aqueous solution was studied in the frog cornea. In general, when the K concentration was increased from 4 to 20 or 79 mM, the transepithelial PD and resistance decreased. If K was decreased from 79 to 4, 20 to 4, or 4 to 0 mM, or any other combination, the PD and resistance increased. These are normal PD responses. If after a K-free period of more than 5-10 min the K was increased to 4 mM, the PD increased, an anomalous PD response. If K was increased from 0 to 20 mM, there was an initial PD increase (anomalous response) followed by a PD decrease (normal response). If K was increased from 0 to 79 mM the PD decreased, normal response only. The resistance decreased with every increase in K concentration. Anomalous responses were abolished in Na-free solutions and in the presence of both 10(-3) M ouabain and 10(-4) M vanadate in the aqueous solution. We interpret the results on the basis of two pathways, a simple K-conductive pathway and an electrogenic Na-K-ATPase pump pathway with more Na's than K's per cycle. The normal or anomalous PD responses to changes in aqueous K concentration depend on the relative resistance of the two pathways.

Effect of loop diuretics on bullfrog cornea epithelium

1989 ◽  
Vol 256 (4) ◽  
pp. C750-C755 ◽  
Author(s):  
W. Nagel ◽  
G. Carrasquer
Keyword(s):  
Apical Membrane ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Loop Diuretics ◽  
Cl Transport ◽  
Before And After ◽  
The Difference ◽  
Cornea Epithelium

The effect of loop diuretics on Cl transport was studied on an in vitro preparation of the bullfrog cornea. Bumetanide (10(-4) M) or furosemide (10(-3) M) added to the stromal solution decreased Cl transport measured as the short-circuit current (Isc) to values near zero. Concomitantly, transepithelial conductance (gt) decreased, whereas the intracellular potential (Vo) hyperpolarized and the fractional resistance of the apical membrane (fRo) increased. Substitution of SO4 for Cl in the tear-side solution led to prompt changes in Isc, gt, Vo, and fRo, characteristic of appreciable passive Cl movement across the apical membrane before and after inhibition. Epinephrine (10(-4) M) was similarly effective on apical membrane conductance in inhibited tissues as under control conditions, but the effective electromotive force for transepithelial Cl transport was reduced to approximately 25%. Intracellular Cl activity, measured with ion-selective microelectrodes, decreased so much that the difference in electrochemical Cl potential divided by the Faraday constant (delta mu Cl/F) was close to zero after inhibition of Isc by bumetanide. Apical Cl permeability remained essentially unchanged. Accordingly, loop diuretics inhibit Cl transport in the Cl-secreting cornea epithelium by blocking the Na-Cl symport without secondary apical effects, as believed for other Cl-reabsorbing epithelia.

Effect of Melittin on Electrophysiological Parameters in the Frog Cornea Epithelium

1996 ◽  
Vol 211 (2) ◽  
pp. 205-210 ◽  
Author(s):  
G. Carrasquer ◽  
S. Yang ◽  
M. Schwartz ◽  
M. A. Dinno
Keyword(s):  
Cornea Epithelium ◽  
Frog Cornea

Effect of Pentachlorophenol (PCP) on Frog Cornea Epithelium

1999 ◽  
Vol 222 (2) ◽  
pp. 139-144
Author(s):  
Gaspar Carrasquer ◽  
Ming Li ◽  
Shen Yang ◽  
Manuel Schwartz ◽  
Mumtaz A. Dinno
Keyword(s):  
Cornea Epithelium ◽  
Frog Cornea

Role of PKC isozymes in water transport in toad urinary bladder

1991 ◽  
Vol 49 ◽  
pp. 302-303
Author(s):  
A.J. Mia ◽  
L.X. Oakford ◽  
T. Yorio
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Membrane Surface ◽  
Protein A ◽  
Cell Types ◽  
Leukemic Cells ◽  
Toad Urinary Bladder ◽  
Pkc Isozymes ◽  
Antibody Labeling

Protein kinase C (PKC) isozymes, when activated, are translocated to particulate membrane fractions for transport to the apical membrane surface in a variety of cell types. Evidence of PKC translocation was demonstrated in human megakaryoblastic leukemic cells, and in cardiac myocytes and fibroblasts, using FTTC immunofluorescent antibody labeling techniques. Recently, we reported immunogold localizations of PKC subtypes I and II in toad urinary bladder epithelia, following 60 min stimulation with Mezerein (MZ), a PKC activator, or antidiuretic hormone (ADH). Localization of isozyme subtypes I and n was carried out in separate grids using specific monoclonal antibodies with subsequent labeling with 20nm protein A-gold probes. Each PKC subtype was found to be distributed singularly and in discrete isolated patches in the cytosol as well as in the apical membrane domains. To determine if the PKC isozymes co-localized within the cell, a double immunogold labeling technique using single grids was utilized.

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