Immunocytochemical localization of metallothionein in human pancreatic islets

Metallothioneins (MTs) are small intracellular proteins that bind to metal ions and are involved in heavy-metal homeostasis and detoxication. Pancreatic islets were previously reported to contain zinc-containing matrix metalloproteinases (MMPs) and inhibitors of metalloproteinases (TIMPs) by immunocytochemical staining. The immunolocalization of MMPs and TIMPs in pancreatic islets prompted us to investigate further the link between zinc and MTs. Both beta and nonbeta islet cells were found to contain MTs by this immunocytochemical staining, suggesting that MTs may be involved in pancreatic hormone synthesis and secretion, in addition to their roles in zinc homeostasis and detoxification.