Melatonin receptor mRNA and protein expression in Xenopus laevis nonpigmented ciliary epithelial cells.
Melatonin is an output signal of the circadian clock, and may regulate diurnal rhythms in ocular tissues. A role for melatonin has been suggested in the circadian changes in intraocular pressure (IOP). Changes in IOP may be due partially to changes in the rate of aqueous humor secretion, which is produced by the nonpigmented epithelium of the ciliary body. To examine the mechanism by which melatonin may influence ciliary epithelium function and perhaps the IOP diurnal rhythm, immunocytochemistry with an antibody directed against the Mel(1c) melatonin receptor subtype was performed on sections of Xenopus eyes. Melatonin receptor immunoreactivity was observed in the basolateral regions of the nonpigmented epithelial cells of the ciliary body. Receptor immunoreactivity was also observed in cells of the retina, as has been previously reported. Specific immunoreactivity was not observed in the epithelium of the iris or pigmented ciliary epithelium. In situ hybridization of the Xenopus eye revealed expression of Mel(1c) but not Mel(1b) receptor mRNA in the nonpigmented ciliary epithelium. These results provide evidence that the nonpigmented epithelia of the ciliary body are direct targets for melatonin, and supports previous work that melatonin may influence the rate of aqueous humor secretion by ciliary epithelium, and perhaps the circadian rhythm of IOP.
Wiechmann
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AF
Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73190, USA. allan-wiechmann@ouhsc.edu
Wirsig-Wiechmann
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CR
D000818:Animals; D002924:Ciliary Body / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D015870:Gene Expression; D017403:In Situ Hybridization; D018613:Microscopy, Confocal; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D044094:Receptors, Melatonin; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014982:Xenopus laevis
D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin