Inhibition of bone resorption in culture by inhibitors of thiol proteinases

Abstract
Leupeptin, antipain, tosyl-lysylchloromethane (Tos-Lys-CH2Cl) and benzyloxycarbonylphenylalanylalanyldiazomethane (Z-Phe-Ala-CHN2) inhibit reversibly the resorption induced by parathyroid hormone or heparin in cultured mouse bones. Leupeptin and antipain do not affect collagenase production and activity or the enhanced secretion of .beta.-glucuronidase induced by the bone-resorbing agents. They might thus act by a direct (extracellular?) inhibition of lysosomal thiol proteinases.