Comparative studies of furosemide effects on membrane potential and intracellular chloride activity in human and rabbit ciliary epithelium.
Furosemide (1 mM), a potent loop diuretic, caused a 10-mV (n = 14) depolarization of the intracellular potential difference (PDI) of isolated rabbit ciliary epithelium (CE), but produced a 9-mV (n = 5) hyperpolarization of PDI of isolated human CE. In rabbit CE, furosemide consistently depolarized PDI by 13, 7 and 8 mV in HCO3(-)-free Ringer, Na(+)-free Ringer and after BaCl2 treatment, respectively. The depolarization of PDI was reduced to 2 mV (n = 11) in Cl(-)-free conditions. A hyperpolarization of PDI caused by furosemide that was quantitatively similar to that seen in normal Ringer also occurred in human CE during immersion in HCO3(-)-free Ringer, Na(+)-free Ringer and after BaCl2 treatment. There was a small hyperpolarization (3 mV) of PDI in Cl(-)-free conditions. Human or rabbit tissue-cultured nonpigmented ciliary epithelial cells were loaded with the Cl(-)-sensitive fluorophore 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ) in hypotonic solution (145 mosm) for 4 min at 37 degrees C. Furosemide decreased intracellular Cl- fluorescence activity of both human and rabbit ciliary epithelial cells by 30 +/- 5 (n = 8) and 25 +/- 7% (n = 13), respectively, when the cells were immersed in Cl(-)-rich solution. It is suggested that a furosemide-sensitive Cl- movement exists in both rabbit and human CE, although the mode of Cl- movement to the aqueous across CE may differ between these species.
Chu
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Department of Ophthalmology, Medical College of Georgia, Augusta 30912-3400.
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D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism*; D002924:Ciliary Body / Q000187:drug effects / Q000378:metabolism*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes; D005665:Furosemide / Q000494:pharmacology*; D006801:Humans; D008253:Macaca mulatta; D008564:Membrane Potentials / Q000187:drug effects*; D008875:Middle Aged; D011806:Quinolinium Compounds; D011817:Rabbits
D002712:Chlorides; D005456:Fluorescent Dyes; D011806:Quinolinium Compounds; D005665:Furosemide; C052335:6-methoxy-N-(3-sulfopropyl)quinolinium