Basic polyaminoacids and protamine stimulate enzyme release from frog muscles

Polylysines, polyornithine, and protamine increased the release of creatine kinase (CK) and lactate dehydrogenase (LDH) from frog muscles. With 5 micrograms/ml (50 nM) of a polylysine of molecular weight 100,000, enzyme release reached peak values (ten-fold above control) within 30 minutes; subsequent removal of the polylysine did not reduce significantly the release rates. The effectiveness of the polycations increased with the degree of polymerization. Their effects were prevented by pretreatment of the muscles with polyanions (heparin or polyglutamic acids) and were reversed when heparin was applied within 30 minutes of exposure to polylysine. The initial stimulation of enzyme release by polylysine was attenuated by Ca-free solutions and by low temperature (4 degrees C). It is suggested that, while fiber damage can explain the increased loss of sarcoplasmic enzymes after prolonged treatment of frog muscles with polycations, other mechanisms (perhaps exocytosis) are involved in the stimulation of CK and LDH release during brief exposures to nanomolar concentrations of polylysines or polyornithine.