Dopaminrezeptoren des Hornhautepithels und -endothels

Zusammenfassung

Hintergrund: Dopamin ist einer der wichtigsten Neurotransmitter des zentralen und peripheren Nervensystems. Während bei Rezeptoren des D1-Subtypes die Signalweiterleitung über einen Anstieg der intrazellulären cAMP Konzentration erfolgt, ist die Signaltransduktion der D2-Rezeptorsubtypen an eine Verminderung der intrazellulären cAMP Produktion gekoppelt. Untersuchungen zum Vorkommen von Dopaminrezeptoren an der Hornhaut sind selten und zum Teil widersprüchlich. Ziel der vorliegenden Untersuchung war es herauszufinden, ob natives, bovines Hornhautepithel und -endothel Dopaminrezeptoren exprimiert, und ob diese zur Gruppe der D1- oder D2-Rezeptorsubtypen gehören.

Material und Methodik: Der Nachweis von Dopaminrezeptoren erfolgte mittels polyklonaler Antikörper. Die Bestimmung der cAMP Konzentration nach Rezeptorstimulation mit Dopamin erfolgte anhand eines handelsüblichen Enzymimmunoassay.

Ergebnisse: Immunhistochemie und Immunfluoreszenz zeigten das Vorkommen von Rezeptoren des D1-Subtypes. Rezeptoren des D2-Subtypes ließen sich an Hornhautepithel oder -endothel nicht nachweisen. Die Stimulation kornealer D1-Rezeptoren führte zu einem dosisabhängigen Anstieg der intrazellulären cAMP Konzentration. Die dopamininduzierte Steigerung der intrazellulären cAMP Produktion konnte durch SCH23 390 (einen selektiven D-1 Rezeptor Antagonisten) verhindert werden.

Schlussfolgerung: Die vorliegenden Ergebnisse zeigen eine Aktivierung der Adenylatzyklase sowie der intrazellulären cAMP Produktion nach Stimulation von Dopamin D1-Rezeptoren in bovinem Hornhautepithel und -endothel. Über die physiologische Rolle dieses Signalweges kann allerdings derzeit nur spekuliert werden.

Abstract

Background: Dopamine is a major neurotransmitter and its two receptor subgroups, termed D1-like and D2-like receptors, are found both in the central and peripheral nervous systems. D1-like receptors signal through increases, D2-like receptors through decreases in cAMP production. Reports about the presence of dopamine receptors in the cornea are rare and inconsistant. The aim of this study was to examine if native bovine corneal epithelial and endothelial cells express dopamine receptors and whether these receptors belong to the D1-like or D2-like group.

Materials and Methods: Dopamine receptors were studied using polyclonal antibodies. The cAMP concentration after receptor stimulation with dopamine was determined by means of an enzyme immunoassay.

Results: In bovine corneal epithelium and endothelium immunohistochemical staining was positive for D1-like receptors but not for D2-like receptors. Stimulation of corneal D1-like receptors with dopamine revealed a dose-dependent increase of the intracellular cAMP concentration which was blocked by SCH23 390 (a selective D1-like antagonist).

Conclusion: Our data demonstrate that bovine corneal epithelium and endothelium express a functional D1-like receptor positively coupled to adenylyl cyclase and cAMP production. However, at the present time the physiological role of this receptor remains a matter of speculation.

Schlüsselwörter

Kornea - Dopamin - Rezeptor

Key words

cornea - dopamine - receptor

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