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Several prostaglandin analogues used for glaucoma treatment cause increased pigmentation of the iris. The purpose of the present study was investigate whether latanoprost, a PGF2ALP analogue, has any effect on the production of endogenous prostaglandins in iridial melanocytes, which could be important in the mechanism leading to increased pigmentation. Bovine and human iridial melanocytes in culture were used for the experiments. Production of endogenous prostaglandins was measured by enzyme immunoassay, and the melanin content was measured spectrophotometrically. In bovine iridial melanocytes, latanoprost acid caused a significant increase of the PGE 2 production, which could be blocked by indomethacin and NS398, indicating an involvement of cyclo-oxygenase 2. In order to study the selectivity of the phenomenon other endogenous substances/drugs were tested, e.g., acetylcholine, carbachol, noradrenaline, neuropeptide Y, substance P and α-MSH, but none was found to have any significant effect. Human iridial melanocytes also responded to latanoprost acid with increased production of PGE2 and in one of five individuals increased melanogenesis coincided with increased PGE2 production. In bovine iridial melanocytes, latanoprost acid did not stimulate melanogenesis. These results indicate that latanoprost acid cause enhanced formation of endogenous prostaglandins that may have auto- and/or paracrine effects in the melanocytes, possibly associated with melanogenesis.
K. Bergh, MD, Department of Neuroscience, Unit of Pharmacology, Biomedical Center, Uppsala University, Uppsala, Sweden. kerstin.bergh@neuro.uu.se
11.4 Prostaglandins (Part of: 11 Medical treatment)