کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6197312 | 1602615 | 2013 | 10 صفحه PDF | دانلود رایگان |

The present study was designed to determine the effects of melatonin and its receptor agonists on SNP-released nitric oxide (NO) and cGMP production in aqueous humor producing cells of the ciliary body because these effects may play a role in melatonin receptor-mediated regulation of intraocular pressure (IOP). NO release protocols were carried out using human non-pigmented ciliary epithelial (hNPCE) cells treated in dye free DMEM containing l-arginine (10â3Â M). The cGMP experimental protocols were performed using dye free DMEM containing 3-isobutyl-1-methylxanthine (IBMX, 10â4Â M). The effects of varying concentrations (10â13, 10â11, 10â9, 10â7, and 10â5Â M) of melatonin, 5-MCA-NAT (putative MT3 agonist), N-butanoyl-2-(2-methoxy-6H-isoindolo[2, 1-a]indol-11-yl)ethanamine (IIK7; selective MT2 agonist) or S-27633-1 (selective MT1 agonist) on sodium nitroprusside (SNP)-released NO or cGMP production were determined in separate experiments. NO and cGMP levels were measured using a colorimetric assay or enzyme immunoassay (EIA), respectively. Melatonin receptor selectivity was evaluated using luzindole (LUZ; nonselective MT1/MT2 antagonist) or 4-phenyl-2-propionamidotetralin (4P-PDOT; selective MT2 antagonist). Melatonin, 5-MCA-NAT, and IIK7 all caused concentration-dependent reduction of SNP-released NO and cGMP production. The inhibitory actions of melatonin, 5-MCA-NAT and IIK7 were either completely blocked at 10â13, 10â11, and 10â9Â M concentrations of the agonists or partially at 10â7 and 10â5Â M in the presence of luzindole or 4P-PDOT. Results from this study suggest that melatonin and its analogs, 5-MCA-NAT and IIK7 inhibit SNP-released NO and cGMP production via activation of MT2 receptors in human NPCE cells. These actions may play a role in melatonin agonist-induced regulation of aqueous humor secretion and IOP.
⺠We demonstrate the functional presence of MT2 melatonin receptors in hNPCE cells. ⺠Melatonin and its congeners inhibit NO release and cGMP production in hNPCE cells. ⺠Possible role of melatonin receptors in the regulation of aqueous humor secretion.
Journal: Experimental Eye Research - Volume 107, February 2013, Pages 1-10