CATIONIC ANTIBIOTICS AND PHOSPHOLIPASE C AS TOOLS IN THE STUDY OF PHOSPHOLIPID STRUCTURE AND FUNCTION: I. INHIBITION OF THE IN VITRO CLOTTING SYSTEM BY CATIONIC ANTIBIOTICS

Abstract

The one-stage prothrombin time of human plasma was prolonged by the addition to the thromboplastic mixture of either colistin sulfate or polymyxin B. Colistimethate sodium, a derivative of colistin in which the amino groups of the cyclic polypeptide antibiotic are substituted, did not show this effect. The inhibition was greater if the antibiotics were incubated with thromboplastin in the absence of Ca++. In the Hicks–Pitney modification of the thromboplastin generation time test, the two polyamine antibiotics reduced the amount of thromboplastic activity generated. Generation, however, appeared to be initiated sooner. It is postulated that these actions by the antibiotics are the results of modifications in the zeta potentials of the thromboplastic micelles.