Alterations of rat serum lipoproteins and lecithin-cholesterol-acyltransferase activity in praseodymium-induced liver damage.

Abstract

During liver damage induced by i.v. injection of 10 mg/kg praseodymium nitrate (Pr) marked alterations of the serum lipids are observed in female Wistar rats. The triglycerides (TG) decrease to about 50% of the control values after 2 days. Total phospholipids (TPL) and cholesterol (C) show a parallel time course: a 50% decrease 2 and 4 days after Pr is followed by a 50% increase at 4 days. The changes in the TPL are mainly due to alterations of phosphatidylcholine (PC) concentration, while the decrease in the concentration of C during the first 2 days is caused by a decrease of the esterified cholesterol (EC), whereas unesterified cholesterol (UC) is responsible for the subsequent increase of C. The fractionation of the serum lipoproteins (Lp) by sequential ultracentrifugation demonstrates a different response to Pr in each Lp class. At 2 days the very low density lipoprotein (VLDL) concentration decreases by 50%. Experiments with Triton WR 1339 show an inhibition of hepatic TG secretion at this time. On the other hand, the LDL increases to more than four times the controls, 4 days after Pr. The accumulating LDL are abnormally rich in UC and PC. Up to 2 days after Pr the high density lipoprotein (HDL) content declines to about 20% of the concentration in control animals. During the subsequent recovery the lipid pattern alters, as UC and TPL are increased; the HDL2 are particularly involved. Concomitant with the changes in the lipid patterns of LDL and HDL the activity of serum lecithin-cholesterol-acyltransferase (LCAT) decreases to about 15%, 3 days after Pr. From our results we conclude: