TY - JOUR
T1 - Blockade of NPE-PE junctional communications by alkanols abolishes active transport by the ciliary body epithelium
AU - Shi, X. P.
AU - Schütte, M.
AU - Candia, O. A.
AU - Wolosin, J. M.
PY - 1996/2/15
Y1 - 1996/2/15
N2 - Purpose. Secretion of aqueous humor (AH) by the ciliary body epithelium (CBE) is believed to result from the cooperation, via gap junctions, of the two distinct cell layers that constitute the CBE. Therefore, disruption of the junctional path between them should block, partially or totally, the secretory activity. The purpose of this study was to test this premise. Methods. Whole rabbit ciliary bodies were mounted in Ussing chambers in Tyrode's under voltage clamp. A negative blood-to-aqueous short circuit current (Isc), which is an electrical expression of the processes driving AH formation, becomes then established (EER 38, 115). The effect of n-alcohols, known junctional inhibitors, on the Isc was then studied. Measured IC50S were converted to inhibitor/ potencies (IP) as PC/IC50, where PC is the lipid:aqueous partition coefficient for each alcohol (Trans Faraday Society, 65, 2645). Additionally, the specificity of these agents for gap junctions was assessed by testing them on other cell functions. Results. Alkanols containing from 5 (C5) to 9 (C9) carbons (i.e., from pentanol to nonyl alcohol) were tested. C5 was inert; all others produced an 80-95% inhibition. The IC50s (in mM) were C6, .18; C7, 1.0; C8, .2; and C9, .07. Relative IP's (C6:C7:C8:C9) were 1:.04:.06:.04. At 1 mM, C6 and C7 had no effect on i) rabbit Na+ + K ATPase; ii) rabbit cell membrane voltage, and iii) baseline intracellular Ca3+; iv its mobilization by adreno-cholinergic agonists. Conclusions. C6-C9 alkanol block specifically gap junctions between the CBE cell layers. Hexanol exhibits, by far, the highest potency. Closing of the junction interrupts active secretion.
AB - Purpose. Secretion of aqueous humor (AH) by the ciliary body epithelium (CBE) is believed to result from the cooperation, via gap junctions, of the two distinct cell layers that constitute the CBE. Therefore, disruption of the junctional path between them should block, partially or totally, the secretory activity. The purpose of this study was to test this premise. Methods. Whole rabbit ciliary bodies were mounted in Ussing chambers in Tyrode's under voltage clamp. A negative blood-to-aqueous short circuit current (Isc), which is an electrical expression of the processes driving AH formation, becomes then established (EER 38, 115). The effect of n-alcohols, known junctional inhibitors, on the Isc was then studied. Measured IC50S were converted to inhibitor/ potencies (IP) as PC/IC50, where PC is the lipid:aqueous partition coefficient for each alcohol (Trans Faraday Society, 65, 2645). Additionally, the specificity of these agents for gap junctions was assessed by testing them on other cell functions. Results. Alkanols containing from 5 (C5) to 9 (C9) carbons (i.e., from pentanol to nonyl alcohol) were tested. C5 was inert; all others produced an 80-95% inhibition. The IC50s (in mM) were C6, .18; C7, 1.0; C8, .2; and C9, .07. Relative IP's (C6:C7:C8:C9) were 1:.04:.06:.04. At 1 mM, C6 and C7 had no effect on i) rabbit Na+ + K ATPase; ii) rabbit cell membrane voltage, and iii) baseline intracellular Ca3+; iv its mobilization by adreno-cholinergic agonists. Conclusions. C6-C9 alkanol block specifically gap junctions between the CBE cell layers. Hexanol exhibits, by far, the highest potency. Closing of the junction interrupts active secretion.
UR - http://www.scopus.com/inward/record.url?scp=33750150343&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:33750150343
SN - 0146-0404
VL - 37
SP - S1107
JO - Investigative Ophthalmology and Visual Science
JF - Investigative Ophthalmology and Visual Science
IS - 3
ER -