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Melatonin binding sites in estrogen receptor‐positive cells derived from human endometrial cancer
Author(s) -
Kobayashi Yoichi,
Itoh Masanori T.,
Kondo Haruhiro,
Okuma Yoshiaki,
Sato Sojiro,
Kanishi Yosuke,
Hamada Naomi,
Kiguchi Kazushige,
Ishizuka Bunpei
Publication year - 2003
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1046/j.1439-0434.2002.00691_2.x-i1
Subject(s) - melatonin , luzindole , melatonin receptor , medicine , endocrinology , receptor , dissociation constant , estrogen receptor , biology , radioligand , chemistry , cancer , breast cancer
Our previous work showed that melatonin ( N ‐acetyl‐5‐methoxytryptamine) inhibits proliferation of the human endometrial cancer cell line, Ishikawa, which is estrogen receptor‐positive. The aim of the present study was to determine whether Ishikawa cells possess membrane melatonin receptors. Binding of the radioligand 2‐[ 125 I]‐iodomelatonin to membrane preparations obtained from Ishikawa cells was detectable, saturable and stable. Scatchard analysis revealed that the dissociation constant ( K d ) of the binding sites was 179.0 p m (similar to that of the MT2 [Mel 1b ] melatonin receptor subtype), and that the concentration ( B max ) of the binding sites was 12.9 fmol/mg protein. Luzindole, a selective MT2 melatonin receptor antagonist, significantly suppressed binding of 2‐[ 125 I]‐iodomelatonin at all concentrations tested (10 −8 to 10 −4 m ). These results suggest that the MT2 melatonin receptor subtype is present in the membranes of Ishikawa cells, and that the antiproliferative effect of melatonin on Ishikawa cells is mediated via the MT2 receptor. This may have implications for the use of melatonin in endometrial cancer therapy.