Gelatinases and inhibitors of gelatinases in pancreatic islets and islet cell tumors.

Pancreatic islets contain trace amounts of zinc to form insulin dimer, and matrix metalloproteinases (MMPs) are single-chain zinc-containing metallo-enzymes. By immunocytochemically staining pancreatic tissue, which contained exocrine duct adenocarcinoma, normal islets were incidentally found positive for gelatinase-A (MMP-2) and gelatinase-B (MMP-9), and for tissue inhibitor of metalloproteinase 1 and 2 (TIMP-1 and TIMP-2). Normal islets from five pancreata were exclusively stained for two each of gelatinases and TIMPs. Twenty-two islet cell tumors were also stained for pancreatic hormones, gelatinases, and TIMPs, which included insulinomas, gastrinomas, glucagonomas, pancreatic polypeptide-omas (PPomas), and nonfunctioning tumor. In general, islet cell tumors were weakly stained for gelatinases and TIMPs, compared with normal islets in the adjacent pancreatic tissue. No clear difference in staining intensity among five kinds of islet cell tumors was observed. The selective immunolocalization of gelatinases and TIMPs in islet cells and islet cell tumors may suggest possible a structure-function relationship among zinc, gelatinases-TIMPs, and pancreatic hormones.