Premium
Characterization of Melatonin Binding Sites in the Pars Tuberalis of the European Hamster
Author(s) -
Skene D. J.,
MassonPévet M.,
Pévet P.
Publication year - 1992
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1992.tb00158.x
Subject(s) - pars tuberalis , melatonin , hamster , medicine , endocrinology , biology , chemistry , pituitary gland , hormone
Melatonin binding sites in the pars tuberalis of the European hamster (Cricetus cricetus) have been characterized using the radioligand 2‐[ 125 I]iodomelatonin. Specific 2‐[ 125 I]iodomelatonin binding was assessed using radioreceptor studies of pars tuberalis membrane preparations. Saturation studies revealed a single, high affinity site (K d 39.8 (± 7.6 SEM) pM and B max 4.1 (± 0.5 SEM) fmol/mg protein, n=4). Kinetic experiments showed the 2‐[ 125 I]iodomelatonin binding to be rapid, saturable and reversible. The K d calculated from the dissociation and association rate constants was 19.4 pM. The order of potency of different indoles for inhibition of 2‐[ 125 I]iodomelatonin binding was 6‐chloromelatonin > melatonin > 6‐hydroxymelatonin > N‐acetylserotonin > 5‐methoxytryptophol > serotonin > 5‐methoxytryptamine. GTP caused a dose‐dependent inhibition of the 2‐[ 125 I]iodomelatonin binding. A saturation study showed that GTP reduced the number of binding sites by a third without altering their affinity. These results imply the presence of a G‐protein‐coupled melatonin receptor in the pars tuberalis of sexually active European hamsters.