Expression of melatonin receptors and 2-[125I]iodomelatonin binding sites in the pituitary of a teleost fish.
The mechanisms of the photoperiodic control of fish physiology (growth, reproduction) and behavior (locomotor activity) are far from being understood. We show here that 2-[125I]iodomelatonin binds specifically to membrane preparations from pike (Esox lucius, L.) pituitaries (KD: 556 pM; Bmax: 2.8 fmol/mg proteins). Radioautography indicated that the binding was restricted to a part of the pituitary only. Using polymerase chain reaction from pike genomic DNA we were able to isolate, subclone and sequence two fragments. The so-called P4 and P8 fragments displayed homology with, respectively, the Mel1a and Mel1b receptor subtypes. The P4 and P8, probes allowed detection of mRNAs corresponding to these receptors in different areas of the brain, including the pituitary. This is the first evidence that melatonin receptors and binding sites are expressed in the pituitary of a non-mammalian species. We suggest that in fish the melatonin-mediated photoperiodic control of neuroendocrine functions might involve a direct effect on the pituitary.
Gaildrat
P
P
Département des Neurosciences, CNRS UMR 6558, Université de Poitiers, France.
Falcón
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001345:Autoradiography; D001483:Base Sequence; D001665:Binding Sites; D002645:Chickens; D003001:Cloning, Molecular; D016384:Consensus Sequence; D017931:DNA Primers; D017859:Esocidae; D006801:Humans; D007457:Iodine Radioisotopes; D008550:Melatonin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D044094:Receptors, Melatonin; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish
D017931:DNA Primers; D007457:Iodine Radioisotopes; D020033:Protein Isoforms; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; C044556:2-iodomelatonin; D008550:Melatonin