Expression of nanomolar-affinity binding sites for melatonin in Syrian hamster RPMI 1846 melanoma cells.
Pharmacological studies indicate that Syrian hamster melanoma (RPMI 1846) cells possess a melatonin binding site similar to that found in normal hamster cells. A high correlation was observed for a series of compounds between the Ki in hamster hypothalamic membranes vs. RPMI 1846 membranes (r = 0.94, slope = 0.93, P less than 0.01, n = 14). Scatchard analysis of saturation binding of 2-[125I]-iodomelatonin to membranes (at 0 degrees C) indicated: Kd = 0.89 +/- 0.08 nM, Bmax = 6.2 +/- 2.9 fmol/mg protein (n = 3). Melatonin did not alter basal or forskolin-stimulated adenylate cyclase activity in RPMI 1846 membranes or intact cells. Therefore, in contrast to the picomolar-affinity receptor for melatonin in the mammalian hypothalamus and pars tuberalis, the putative nanomolar-affinity receptor is not coupled to adenylate cyclase. The RPMI 1846 cell line provides a useful model system for further studies of signal transduction via the nanomolar-affinity site for melatonin.
Pickering
D S
DS
Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Niles
L P
LP
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D006224:Cricetinae; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D008546:Melanoma, Experimental / Q000201:enzymology / Q000378:metabolism*; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism*; D008647:Mesocricetus; D011485:Protein Binding; D014407:Tumor Cells, Cultured
D003470:Culture Media; C044556:2-iodomelatonin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D008550:Melatonin