Characterization of a putative calcitonin receptor in IMR 32 human neuroblastoma cells

In this study we characterized calcitonin (CT) receptors in human neuroblas toma IMR 32 cells. Saturation binding assays indicated that [I-125]-human C T bound with high affinity to IMR 32 cell membranes (K-d = 253.6 PM; B-max = 3.84 fmol/ mg protein). In competition binding studies, human adrenomedul lin displayed high affinity for these sites (IC50 = 30 nM) whereas human al pha calcitonin-gene related peptide (alpha CGRP; IC50 = 145 nM) and human a mylin (IC50 = 415 nM) showed lower affinity. These peptides increased cAMP levels in viable cells; the relative potencies were: human CT > human adren omedullin > human alpha CGRP greater than or equal to human amylin. The exp ression of mRNA coding for the published sequences of the human calcitonin receptor and of the human calcitonin receptor-like receptor was evaluated b y reverse transcriptase-polymerase chain reaction. Electrophoretic analysis did not confirm the occurrence of mRNA coding for the above mentioned rece ptors in these cells. This study suggests the presence of a novel, putative CT receptor in IMR 32 cells. (C) 1999 Elsevier Science Ireland Ltd. All ri ghts reserved.