N-Isopropyl-p-iodoamphetamine receptors in normal and cancerous tissue of the human lung |
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Authors: | Eiko Tanaka Michiaki Mishima Kenzo Kawakami Naoki Sakai Naoharu Sugiura Takashi Taniguchi Kenshi Kuno |
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Affiliation: | (1) Department of Clinical Physiology, Chest Disease Research Institute, Kyoto University, 53 Shogoin Kawahara-cho, Sakyoku, 606 Kyoto, Japan;(2) Department of Neurobiology, Kyoto Pharmaceutical University, 607 Kyoto, Japan |
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Abstract: | N-Isopropyl-p-iodoamphetamine (IMP) receptors in normal human lung tissue were characterized using a radioligand binding assay with iodine-125 IMP as the ligand. Saturation binding studies revealed the presence of two binding sites with dissociation constant (Kd) values of 53 ± 2 and 4687 ± 124 nM and maximum binding capacity (Bmax) values of 7 ± 1 and 133 ± 27 pmol/mg protein (n=5) respectively. The IC50 values of various amines were as follows: IMP, 9 × 10–5M; propranolol, 5 × 10–4M; haloperidol, 6 × 10–4M; ketamine, 9 × 10–3M; dopamine, 1 × 10–2M. The IMP receptors of cancerous tissue obtained from human lung also had two binding sites with Kd values of 54 ± 2 and 5277 ± 652 nM and Bmax values of 7±1 and 103 ± 21 pmol/mg protein (n = 3) respectively. There was no significant difference in binding parameters between normal and cancerous lung tissue. These results demonstrate the existence of IMP receptors and suggest that cancer does not affect the nature of IMP receptors in human lung tissue.Correspondence to: E. Tanaka |
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Keywords: | N-Isopropyl-p-iodoamphetamine (IMP) Iodine-123-IMP Iodine-125-IMP IMP binding IMP receptors (human lung) |
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