In vitro response of atpase activities in tissue subcellular particle preparations to a series of mono-unsaturated C 18 fatty acids

Abstract

The positions of the double bond and the cis/trans configurations of six mono-unsaturated C 18 fatty acids (FA) showed selectivity for inhibition and stimulation of ATPase activities of tissue homogenate fractions. The 13,000 g and 100,000 g sediments (fractions B and C respectively) of tissue homogenates were used as sources of Na +−K + ATPase and of oligomycin-sensitive (OS) and -insensitive (OIS) Mg 2+ ATPase activities. Tissue sources included bovine brain and rat brain, kidney, heart and liver. Cis mono-unsaturated C 18 FA caused an apparent uncoupling of mitochondrial coupling factor F 1 (Mg 2+ ATPase). This was indicated by the loss of oligomycin and 1,1,1-trichloro-2,2 bis ( p-chlorophenyl) ethane (DDT) sensitivity in the presence of 50 μM FA (12-C 18:1). Thus, a precipitous decrease in OS-Mg 2+ ATPase activity of mitochondria was accompanied by an equally steep increase in OIS-Mg 2+ ATPase activity. This was especially apparent in a heart tissue preparation. The uncoupling action of the FA was not observed with the trans mono-unsaturated C 18 FA. Na +−K + ATPase activity from a bovine brain nerve ending particle (B) fraction was also sensitive to 12−C 18:1FA. However, inhibitory responses of Na +−K + ATPase activity were different for OS-Mg 2+ ATPase activity. The latter (OS) was not sensitive to the trans 12-C 18:1, while the former (Na +−K +) was sensitive to both cis and trans forms of 12-C 18:1 and inhibition appeared to be dependent on the position of the double bond.