Blood samples were collected into 10 ml S-monovette tubes
(Sarstedt, Nuemrecht, Germany) containing sodium EDTA
as anticoagulant. After clotting, plasma was prepared by centrifugation
(10 min; 48C) at 3800 g and stored at 2808C until
analysis. Lipids were extracted according to Folch & Lees(16)
with slight modifications. Plasma sample (0·5 ml) was placed
in a 10ml glass tube and mixed with 5ml chloroform–methanol
(2:1), containing 200 mg/l butylated hydroxytoluene
(BHT) as antioxidant. The sample was mixed by shaking
at 378C for 45 min. After addition of 1ml sodium chloride
solution (0·9 %) and centrifugation at 660 g for 10 min at
48C, the lipophilic layer was collected and washed twice