The influence of pluronics and their conjugates with proteins on the rate of oxygen consumption by liver mitochondria and thymus lymphocytes

Abstract

The membranotropic properties of block co‐polymers and their protein conjugates were studied by their effect on the rate of oxygen consumption by isolated liver mitochondria and on thymus‐derived lymphocytes. The block co‐polymers consisted of poly(ethylene oxide) (PoE) [poly(ethylene glycol)] and poly(propylene oxide) (PoP) to give either PoE‐PoP or PoE‐PoP‐PoE. Both types inhibited uncoupled respiration of liver mitochondria in a medium containing glutamate and malate and also of lymphocytes. They also uncoupled respiration in the presence of succinate in K(+)‐containing medium and of lymphocytes. A method is described for linking protein to the block polymers to form conjugates. Such conjugates were formed from alpha‐chymotrypsin, BSA and cytochrome c, all of which produced similar effects on the respiration of the isolated mitochondria and lymphocytes. The data suggest that both the block co‐polymers and their protein conjugates inhibit the NADH dehydrogenase complex and induce a K(+)‐conductivity of the mitochondrial inner membrane; the surface activity of the conjugates allows them to pass through the plasma membrane and interact with the mitochondrial inner membrane.