[Properties of protamine-heparin complexes].

Protamine-heparin complexes have a considerable resistance to physical factors of the environment such as a high ion strength and acid or alkaline pH. Free protamine is digested by plasmin giving products with a greatly decreased ability to form complexes with heparin and lower antiheparin action. Bound protamine, on the other hand, is resistant to the action of plasmin as a result of which the enzyme does not release heparin from the complexes.