SERUM PARAOXONASE ACTIVITY IS DECREASED IN UREMIC PATIENTS

Paraoxonase is a high-density lipoprotein (HDL)-associated enzyme capa ble of hydrolysing lipid peroxides. We measured the activity of serum paraoxonase together with serum concentrations of a variety of lipid c onstituents - total cholesterol, high-density lipoprotein (HDL) and lo w-density lipoprotein (LDL), cholesterol, triglycerides, apolipoprotei ns A-I and B- in 60 hemodialyzed (HD) patients. We found that the para oxonase activity was significantly reduced in HD patients compared wit h 64 healthy controls (mean median and interquartile values: 93, 63, 8 7 IU/l in HD patients and 151, 120 and 135 IU/l in controls). In patie nts, the trimodal frequency of distribution of paraoxonase activity sh owed a shift toward lower levels. The effect of NaCl on enzyme activat ion was more pronounced in the patient group, as compared with control s, suggesting a higher frequency of the B allozyme (more responsive to NaCl) in this population. We suggest that altered HDL subfraction, pr esent in HD patients, may be the main cause of the widespread depressi on of paraoxonase. Furthermore, the higher frequency of allozyme B amo ng HD patients might increase the risk of coronary artery disease. In conclusion, paraoxonase activity may be an adjunctive index of altered lipoprotein metabolism with important repercussions on atherosclerosi s.