Melatonin Research Research Articles

Detection and quantification of melatonin in a dinoflagellate, Gonyaulax polyedra: Solutions to the problem of methoxyindole destruction in non‐vertebrate material

Preservative procedures are described for the extraction and quantification of melatonin in cell material from the dinoflagellate Gonyaulax polyedra, an organism in which this indoleamine is rapidly degraded due to interaction with free oxygen radicals and photooxidation. Cells were shock-frozen in liquid nitrogen and pulverized. Various extraction methods were applied to the powder, and rates of recovery were compared. For the determination of melatonin by high performance liquid chromatography (HPLC), extractions with acetone or perchloric acid were more suitable than the use of other solvents. For purposes of radioimmunoassay (RIA), extraction with acetone gave the best results. Several other inorganic solvents, which are often applied in melatonin research, such as chloroform, dichloromethane, and diethyl ether, led to considerable losses of the indoleamine. The procedures developed for HPLC with either electrochemical or fluorescence detection also allow the quantification of other indolic compounds, in particular, tryptophan and 5-methoxytryptamine. The methods described may be of value in the further search for melatonin and related indoleamines in non-vertebrate material, especially, from unicells, multicellular plants, and invertebrates.

Melatonin receptors in peripheral tissues: a new area of melatonin research.

Melatonin is synthesized and secreted by pineal gland, retina, harderian gland, lacrimal gland, and gut. It is a lipid-soluble molecule with ubiquitous distribution and multifarious functions. Thus, along with the better established sites of melatonin action, such as brain, retina, and pituitary, direct melatonin actions on other peripheral tissues should also be considered. The presence of melatonin receptors in peripheral tissues was rightfully hypothesized. Earlier studies on melatonin receptors had limited success. The advent of 2-[125I]iodomelatonin, a labelled melatonin agonist with a specific activity as high as 2,200 Ci/mmol, has allowed the studies of melatonin receptors with picomolar affinity and femtomolar density. Putative melatonin receptors demonstrated by autoradiography and/or radioreceptor assay in gut, kidney, lung, heart, vas deferens, and blood vessels are discussed.