[Mechanism of opiate-induced permeability of mitochondrial membranes for potassium ions]

Abstract

Incubation of isolated rat liver mitochondria in the presence of morphine or its derivatives--methylmorphine, tecodine, ethylmorphine and nalorphine--results in disturbances of oxidative phosphorylation due to induction of permeability of mitochondrial membranes for potassium ions. The rate of state 4 respiration of rat liver mitochondria in the presence of opiates is increased only in a medium containing potassium ions. The opiates induce the efflux of K+ from deenergized mitochondria and accumulation of free fatty acids in mitochondria. However, morphine derivatives do not alter the permeability for potassium and electrical conductibility of artificial phospholipid membranes. It was suggested that opiates cause a formation of the potassium carrier in mitochondria by releasing Ca2+, which activate phospholipase A2. The effect of opiates increases with the increase of their hydrophobic properties.