Cl- secretory effects of EBIO in the rabbit conjunctival epithelium

• Published in: American Journal of Physiology: Cell Physiology Vol. 58; no. 1; pp. C138 - C147
• Main Authors: ALVAREZ, Lawrence J, ZAMUDIO, Aldo C, CANDIA, Oscar A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Physiological Society 01.07.2005
• Subjects: Biological and medical sciences; Body fluids; Cell physiology; Cells; Eyes & eyesight; Fundamental and applied biological sciences. Psychology; Membrane and intracellular transports; Molecular and cellular biology; Potassium; Rabbits; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; 1-ethyl-2-benzimidazolinone; Biological transport; Rabbit; Ussing chamber; potassium conductance; Lagomorpha; Epithelium; short-circuit current; electrolyte transport; chloride secretagogue; Vertebrata; Mammalia; Electrolyte; Chlorides; 1,10-phenanthroline; Potassium
• ISSN: 0363-6143; 1522-1563

Experiments were conducted to determine whether the Cl- secretagogue, 1-ethyl-2-benzimidazolinone (EBIO), stimulates Cl- transport in the rabbit conjunctival epithelium. For this study, epithelia were isolated in an Ussing-type chamber under short-circuit conditions. The effects of EBIO on the short-circuit current (Isc) and transepithelial resistance (Rt) were measured under physiological conditions, as well as in experiments with altered electrolyte concentrations. Addition of 0.5 mM EBIO to the apical bath stimulated the control Isc by 64% and reduced Rt by 21% (P < 0.05; paired data). Under Cl--free conditions, Isc stimulation using EBIO was markedly attenuated. In the presence of an apical-to-basolateral K+ gradient and permeabilization of the apical membrane, the majority of the Isc reflected the transcellular movement of K+ via basolateral K+ channels. Under these conditions, EBIO in combination with A23187 elicited nearly instantaneous 60-90% increases in Isc that were sensitive to the calmodulin antagonist calmidazolium and the K+ channel blocker tetraethyl ammonium. In the presence of an apical-to-basolateral Cl- gradient and nystatin permeabilization of the basolateral aspect, EBIO increased the Cl--dependent Isc, an effect prevented by the channel blocker glibenclamide (0.3 mM). The latter compound also was used to determine the proportion of EBIO-evoked unidirectional 36Cl- fluxes in the presence of the Cl- gradient that traversed the epithelium transcellularly. Overall, EBIO activated apical Cl- channels and basolateral K+ channels (presumably those that are Ca2+ dependent), thereby suggesting that this compound, or related derivatives, may be suitable as topical agents to stimulate fluid transport across the tissue in individuals with lacrimal gland deficiencies. [PUBLICATION ABSTRACT]