Cyclic AMP‐Dependent Melatonin Production in Y79 Human Retinoblastoma Cells

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Abstract
Melatonin is rhythmically synthesized in some vertebrate retinas and has been implicated in the regulation of key rhythmic events in the photoreceptor‐pigment epithelial complex. In human retina, melatonin is present; however, no information exists on the cellular regulation of this hormone. We report here that the established human retinoblastoma cell line Y79 synthesizes and releases melatonin. Treatments that elevate cyclic AMP (cAMP) levels (forskolin, 8‐Br‐cAMP, and the phosphodiesterase inhibitor 3‐isobutyl‐1 ‐meth‐ylxanthine) all stimulate melatonin release from static cultures of Y79 cells. Other 8‐bromo nucleotide analogues (cyclic GMP, ATP, and AMP) are not effective. These results suggest that Y79 human retinoblastoma cells require a cAMP‐dependent mechanism for melatonin biosynthesis similar to that described previously in other vertebrates. This is the first demonstration of melatonin release from a cultured human cell line. These results support the idea that human retinal cells share homologies with pineal cells, as suggested by the condition trilateral retinoblastoma.