Meprin Phenotype and Cyclosporin A Toxicity in Mice

Meprin is a membrane-bound metallo-proteinase that is present in high concentrations in the kidney brush border of mice and rats (Bond and Beynon, 1986). The enzyme has been purified and found to exist as a tetrameric glycoprotein that contains one mol zinc and three mol calcium per 85,000 molecular weight subunit (Beynon et al., 1981; Butler et al., 1987). Meprin hydrolyzes a variety of peptide and protein substrates (e.g., insulin B chain, glucagon, angiotensins I and II, bradykinin, hemoglobin, casein, aldolase, and phosphorylase kinase); the substrate used most often to assay activity is azocasein, a good general substrate for neutral and alkaline proteinases.