Lipid peroxidation, as measured by the thiobarbituric acid test, has b
een reported to have increased in hemodialysis (HD) patients, even tho
ugh the test has low specificity in vivo. Conjugated diene fatty acid
(CDFA) hydroperoxides are formed during lipid peroxidation, but not al
l conjugated dienes (CD) detected in humans originate from lipid perox
idation: octadeca-9,11-dienoic acid, a nonhydroperoxide CD derivative
of linoleic acid (CDLA), has a dietary origin. We evaluated CDFA hydro
peroxides, CDLA and linoleic acid, using high-performance liquid chrom
atography, in lipids extracted from plasma, adipose tissue and RBC mem
branes obtained from 25 patients treated with HD, 16 patients treated
with hemodiafiltration (HDF) and 29 controls. No differences in the le
vels of CDFA hydroperoxides and linoleic acid were seen in any of the
groups. Concentrations of CDLA were found to be significantly high in
the adipose tissue and low in the RBC membranes of HD patients. HDF-tr
eated patients showed the same results as HD patients. No direct evide
nce of increased lipid peroxidation was found in HD patients. This doe
s not exclude the possibility that lipid peroxidation is increased and
escapes direct detection due to the body's homeostatic control elimin
ating the increased production of hydroperoxides. Both HD- and HDF-tre
ated patients showed a significant change in CDLA concentrations, eith
er in the adipose tissue, or in the RBC membranes. These dietary CD ma
y be mistaken for markers of lipid peroxidation by conventional method
ologies.