Insulin-like growth factor-I activates a calcium-permeable cation channel GRC (growth factor-regulated channel). In the present study, we investigated the immunohistochemical localization of GRC in human tissues using a polyclonal anti-GRC antibody. Immunoreactive GRC was detected in the stomach, duodenum, large intestine and prostate. In these tissues, GRC-expressing cells were distributed solitarily in the epithelium and coexpressed chromogranin-A, a marker of neuroendocrine cells. GRC was also expressed in the epithelium of the pancreatic duct, mammary gland, parotid gland, and submandibular gland. Epithelial cells of the renal tubule and the tracheal gland were also stained with anti-GRC antibody. In the lung, alveolar macrophages expressed GRC. In the brain, Purkinje cells of the cerebellum and arachnoid cells of the meningis expressed GRC. These results indicate that GRC is expressed in restricted types of cells in particular tissues, and that GRC may modulate calcium entry in these cells.