Stimulation of Succinate Conversion to CO2 by Supernatant Fluid from Corneal Epithelium

Forskolin (and other Cl- secretagogues) does not affect the very small Na(+)-originated short-circuit current (Isc) across frog corneal epithelium bathed in Cl- free solutions. However, forskolin in combination with increased PCO2 bubbling of the solutions (5-20% CO2) stimulated Isc proportionally to PCO2 to a maximum of approximately 8 microA/cm2. This current could be eliminated and reinstated by sequentially changing the gas composition of the bubbling to 100% air and 20% CO2-80% air. The same effects were observed when PCO2 changes were limited to the apical-side solution. Stroma-to-tear HCO3- movement was deemed unlikely, since the increase in Isc was observed with a HCO3(-)-free solution on the stromal side and CO2 gassing limited to the tear side. From the effects of ouabain and tryptamine, at least 80% of the Isc across the basolateral membrane can be accounted for by the Na+ pump current plus K+ movement from cell to bath. Methazolamide also inhibited Isc. Current across the apical membrane cannot be attributed to an electronegative Na(+)-HCO3- symport given the insensitivity of Isc to a disulfonic stilbene and the fact that stroma-to-tear Na+ fluxes did not increase on stimulation of Isc. The tear-to-stroma Na+ flux also remained unaltered, negating an increased apical bath-to-cell Na+ flow. The forskolin-20% CO2 manipulation produced a depolarization of the intracellular potential, a reduction in the apical-to-basolateral resistance ratio, and a decrease in transepithelial resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

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Stimulation of partial development of human mast cells by supernatant fluid from mouse fibroblast cultures

Clinical & Experimental Allergy ◽

10.1111/j.1365-2222.1994.tb00969.x ◽

1994 ◽

Vol 24 (7) ◽

pp. 649-659 ◽

Cited By ~ 10

Author(s):

A. M. DVORAK ◽

H. MITSUI ◽

T. ISHIZAKA

Keyword(s):

Mast Cells ◽

Mouse Fibroblast ◽

Supernatant Fluid ◽

Human Mast Cells ◽

Fibroblast Cultures ◽

Stimulation Of

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Stimulation of ion transport by ascorbic acid through inhibition of 3′:5′-cyclic-AMP phosphodiesterase in the corneal epithelium and other tissues

Biochimica et Biophysica Acta (BBA) - Biomembranes ◽

10.1016/0005-2736(75)90319-3 ◽

1975 ◽

Vol 389 (2) ◽

pp. 251-260 ◽

Cited By ~ 19

Author(s):

Marion Gilmour Buck ◽

J.A. Zadunaisky

Keyword(s):

Ascorbic Acid ◽

Cyclic Amp ◽

Ion Transport ◽

Corneal Epithelium ◽

Cyclic Amp Phosphodiesterase ◽

Stimulation Of

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Cholinergic stimulation of phosphatidylinositol hydrolysis by rat corneal epithelium in vitro

Current Eye Research ◽

10.3109/02713688709034832 ◽

1987 ◽

Vol 6 (5) ◽

pp. 691-701 ◽

Cited By ~ 14

Author(s):

Keith H. Baratz ◽

Alan D. Proia ◽

Gordon K. Klintworth ◽

Eduardo G. Lapetina

Keyword(s):

Corneal Epithelium ◽

Cholinergic Stimulation ◽

Stimulation Of

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Forskolin effects on frog and rabbit corneal epithelium ion transport

AJP Cell Physiology ◽

10.1152/ajpcell.1986.251.3.c448 ◽

1986 ◽

Vol 251 (3) ◽

pp. C448-C454 ◽

Cited By ~ 25

Author(s):

O. A. Candia ◽

L. R. Grillone ◽

T. C. Chu

Keyword(s):

Corneal Epithelium ◽

Rana Catesbeiana ◽

Apical Membrane ◽

Short Circuit ◽

Control Level ◽

Short Circuit Current ◽

Potential Difference ◽

Ionophore A23187 ◽

Intracellular Recordings ◽

Stimulation Of

The effects of forskolin on the electrophysiological parameters of the isolated corneal epithelium from bullfrog (Rana catesbeiana) were investigated. Forskolin stimulated the short-circuit current (SCC) and transepithelial potential difference (PDt), while reducing the transepithelial resistance. These effects were absent in Cl- -free bathing solutions. Furosemide, added either before or after forskolin, completely blocked the effects. Epinephrine and A23187, added after forskolin, produced only a small additional stimulation of the SCC. Propranolol neither blocked nor reduced the effect of forskolin. Forskolin increased the stroma to tear 36Cl flux by 61% and the tear to stroma 36Cl flux by 64%. Intracellular recordings showed that forskolin depolarized the potential difference across the apical membrane and reduced the apical/basolateral resistance ratio. Intracellular recordings in the isolated rabbit epithelium showed the same effects by forskolin except that there was only a brief stimulation of PDt, after which it stabilized slightly below the control level. These results are consistent with an increase in apical membrane permeability similar to that produced by adenosine 3',5'-cyclic monophosphate, epinephrine, and the Ca2+ ionophore A23187.

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