Transepithelial Short Circuit Currents in Human and Porcine Isolated Ciliary Bodies: Effect of Acetazolamide and Epinephrine

Zusammenfassung

Hintergrund: Die vorliegende Studie untersucht den Effekt von Acetazolamid und Epinephrin auf den transepithelialen Ionenfluss (ein Parameter, der die Kammerwasserproduktion widerspiegelt) im Ziliarkörper des Menschen und des Schweines. Material und Methoden: Isolierte Ziliarkörper wurden in einer Ussing-Kammer eingespannt, um die transepitheliale Potenzialdifferenz (PD) und die Kurzschlussströme (Isc) vor und nach Exposition mit 100 µM Acetazolamid oder 10 µM Epinephrin zu messen. Resultate: In menschlichen Ziliarkörpern (n = 27), war die Basislinien-PD (1184 ± 100 µV) auf der unpigmentierten Epithelium(NPE)-Seite negativ, der entsprechende Isc betrug 19,9 ± 1,5 µA/cm². Acetazolamid (n = 7 - 8) erniedrigte Isc (NPE-Seite 8,4 ± 1,1 µA/cm², pigmentierten Epithelium [PE]-Seite 7,4 ± 0,9 µA/cm²). Epinephrin (n = 6) erniedrigte den Isc nur auf der NPE-Seite um 9,9 ± 0,8 µA/cm². Im Schweineziliarkörper war die Basislinien-PD in einigen Präparaten negativ (862 ± 84 µV, n = 18) und in anderen positiv (814 ± 81 µV, n = 10) auf der NPE-Seite mit Isc (15,6 ± 1,6 µA/cm², respektive 16,3 ± 2,6 µA/cm²). In allen Präparaten erniedrigte Acetazolamid (n = 6 - 7) den Isc (NPE-Seite: 6,1 ± 0,6 µA/cm²; PE-Seite: 4,8 ± 0,3 µA/cm²), wogegen Epinephrin (n = 8) Isc nur auf der NPE-Seite (10,5 ± 0,6 µA/cm²) erhöhte. Schlussfolgerungen: In der vorliegenden Studie wurde erstmalig die Ussing-Kammer zur Messung von transepithelialen Ionenströmen am isolierten Ziliarkörper des Menschen und des Schweines verwendet. Eine zukünftige Anwendungsmöglichkeit der Methode liegt in der Untersuchung von Medikamenten, die die Kammerwasserproduktion beeinflussen.

Abstract

Background: To investigate in human and porcine isolated ciliary bodies the effect of acetazolamide and epinephrine on ciliary transepithelial ionic currents (a parameter linked to aqueous humor production). Material and methods: Isolated ciliary bodies were mounted in a Ussing-type chamber to measure transepithelial potential difference (PD) and short circuit current (Isc) before and after exposure to either 100 µM acetazolamide or 10 µM epinephrine. Results: In humans (N = 27), baseline PD was 1184 ± 100 µV (negative on the non-pigmented epithelial [NPE] side) and Isc 19.9 ± 1.5 µA/cm². Acetazolamide (N = 7 - 8) decreased Isc (NPE side: 8.4 ± 1.1 µA/cm²; pigmented epithelial [PE] side: 7.4 ± 0.9 µA/cm²) while epinephrine (N = 6) increased Isc only on the NPE side (9.9 ± 0.8 µA/cm²). In pigs, baseline PD was in some preparations negative (862 ± 84 µV, N = 18) and in others positive (814 ± 81 µV, N = 10) on the NPE side with Isc 15.6 ± 1.6 µA/cm² and 16.3 ± 2.6 µA/cm², respectively. In all preparations, acetazolamide (N = 6 - 7) decreased Isc (NPE side: 6.1 ± 0.6 µA/cm²; PE side: 4.8 ± 0.3 µA/cm²) while epinephrine (N = 8) increased it only on the NPE side (10.5 ± 0.6 µA/cm²). Conclusions: To our knowledge, this is the first time that this methodology is applied to measure transepithelial ionic currents in isolated human and porcine ciliary bodies. This method could be used to test drugs modulating aqueous humor production.

Schlüsselwörter

Glaukom - Ziliarkörper - Kurzschlussstrom - Karbonanhydrase Inhibitor - Adrenorezeptoragonist

Key words

Glaucoma - ciliary process - short circuit current - carbonic anhydrase inhibitors - adrenoreceptor agonists

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