Characterization of beta-adrenergic receptors in DiFi and HT-29 cells
Abel, P.W.; Zeng, W.; Wildrick, D.M.; Makoid, M.C.; Boman, B.M.
Anticancer Research 12(5): 1655-1658
1992
ISSN/ISBN: 0250-7005 PMID: 1359831 Document Number: 399415
The beta-adrenergic receptors present in two human colorectal adenocarcinoma cell lines were characterized by measuring specific binding of (125I)-cyanopindolol (CYP). Whole, cultured, DiFi (derived from a familial adenomatous polyposis (FAP) patient) and HT-29 cells were used in radioligand binding assays. Scatchard analysis of specific 125I-CYP binding gave K-DS of 38.6 +- 5.7 pM in DiFi cells and 54 +- 9.1 pM in HT-29 cells. However, binding site density (B-max) in the DiFi cells was greater than that in HT-29 cells. In DiFi cells, the kinetically determined K-D was similar to that calculated from Scatchard analysis. Studies in DiFi cells of the displacement of specific 125I-CYP binding by nonselective (propranolol), beta-1-selective (metoprolol and atenolol), and beta-2-selective (ICI 118-551) antagonists revealed only a single class of beta-2-adrenergic receptors. This provides the first evidence that colorectal adenocarcinoma cell lines contain beta-adrenergic receptors and shows that only beta-2-adrenergic receptors are present in DiFi cells. Mechanisms possibly affecting beta-adrenergic-receptor expression in such cells are discussed in relation to colon carcinogenesis.