ATP-ase activity of mitochondria isolated from needle-biopsy liver samples of diabetic subjects.

ATP-ase activity in mitochondria isolated from liver needle-biopsy samples was measured in 5 diabetics, aged 30-63 years and in 4 control subjects of similar age. The mitochondrial fraction was isolated by differential centrifugation of the homogenate and the ATP-ase activity was determined in the optimal conditions previously described for human liver mitochondria. The basal and Mg-stimulated ATP-ase activities were higher, while the DNP-stimulated ATP-ase activity was lower in diabetics compared to controls. The ratio of DNP-ATP-ase/Mg2+-ATP-ase was between 1-2 in diabetics and above 5 in controls. This pattern of ATP-ase activity in diabetics is indicative of mitochondrial damage. No quantitative changes in the amount of mitochondria isolated from liver (expressed in micrograms mitochondrial protein/mg wet tissue) could be noticed in diabetics compared to controls. Consequently, the alterations of ATP-ase activity is probably reflective of impairments of functional integrity of liver mitochondria in diabetics.