Retinal and pineal hydroxyindole-o-methyl transferase activity in vertebrates

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…The rat pineal HIOMT activity is between 0.7 and 2 nmol/mg protein/h (Sugden et al, 1987b;Ribelayga et al, 1997Ribelayga et al, , 1998bRibelayga et al, , 1999a. HIOMT activity has been measured in the retina and the Harderian gland, although at much lower levels (Quay, 1965;Cardinali and Rosner, 1971;Cardinali and Wurtman, 1972;Nagle et al, 1972Nagle et al, , 1973Pévet et al, 1980a;Wiechmann and Hollyfield, 1989;Bernard et al, 1995;Gauer and Craft, 1996;Djéridane et al, 1998;Ribelayga et al, 1998a). Enzyme studies suggest that the pineal and retina HIOMT are similar, but quite different from HIOMT in the Harderian gland (Cardinali and Wurtman, 1972).…”

“…Autocrine/Paracrine Effects. In addition to the pineal gland, MEL is synthesized in several other structures (retina, Harderian gland, gut) where the genetic expression and biochemical activity of the MEL-synthesizing enzymes have been detected (Quay, 1965;Cardinali and Wurtman, 1972;Quay and Ma, 1976;Brammer et al, 1978;Pévet et al, 1980a;Vivien-Roels et al, 1981;Gauer and Craft, 1996;Roseboom et al, 1996;Ribelayga et al, 1998a;Djéridane et al, 1998Djéridane et al, , 2000. Since following pinealectomy the plasma MEL concentration is very low and since some of these structures contain MEL-R (Dubocovich and Takahashi, 1987;Lopez-Gonzalez et al, 1991), it has been proposed that MEL plays an auto/paracrine role in these structures.…”

Multioscillatory Circadian Organization in a Vertebrate,Iguana iguana

“…Although it has previously been suspected of producing melatonin (Quay, 1965;Firth and Kennaway, 1987), ours is the first unequivocal demonstration of this capacity. The observation that melatonin is synthesized under the control of circadian oscillators within the parietal eye is also unique.…”

“…The lateral eyes of the frog Xenopus laevis, chicken, quail, fish (Esox lucius), and mammals also contain self-sustained circadian oscillators that regulate melatonin synthesis (for review, see Cahill and Besharse, 1995; also see Menaker and Tosini, 1996;Tosini and Menaker, 1996a). Although there is evidence suggesting that the parietal eye of some lizards may synthesize melatonin (Quay, 1965;Firth and Kennaway, 1987), this structure has never been studied in vitro to test for the capacity to synthesize melatonin and for the presence of circadian oscillators.…”

The pineal gland of the mole (Talpa europaea, L.). V) Activity of hydroxyindole-O-methyl transferase (HIOMT) in the formation of melatonin/5-methoxytryptophol in the eyes and the pineal gland

“…Subsequently it was identified in the mammalian retina Rosner, 1971, 1972 ;Quay, 1965) (Pevet and Collin, 1976 ;Pevet et al, 1977) that the pinealocytes of mammals belong to a sensory cell line that has evolved from sensory pineal photoreceptors of lower vertebrates during phylogenetic development (Collin, 1969(Collin, , 1971 Quay (1974) wrote : « It is probably safe to assume that melatonin occurring in these and other mammalian tissues and fluid (the peripheral nerves, blood and urine) is derived from the pineal gland, because of the pineal localization of the enzyme responsible for the last step in melatonin's biosynthesis, and because of the above cited loss of melatonin from chicken serum after pinealectomy. There is no evidence as yet that the low levels of this enzyme, hydroxyindole-0-methyltrcinsferase, detectable in retina and Harderian gland can contribute to a release of melatonin from these other tissues.…”