HYPERLIPOPROTEINEMIA IN ONE-YEAR-OLD ANALBUMINEMIC RATS

Plasma lipoprotein distribution and apolipoprotein concentrations, as well as kidney function and histopathology of heart, aorta, liver and kidney were investigated in 1-year-old Nagase analbuminemic rats (NAR) and control Sprague-Dawley rats (SDR). The NAR, particularly the females, were found to be severely hyperlipidemic. Plasma total cholesterol in non-fasted animals was 6.1 +/- 0.3 mM in the female NAR vs. 2.5 +/- 0.2 mM in the female SDR (P < 0.01). Most of the cholesterol was located in the LDL (1.019 - 1.063 g/ml) and HDL2 (1.063 - 1.125 g/ml) density range. Plasma triglycerides were 6.1 +/- 0.6 mM in the female NAR vs. 1.3 +/- 0.3 mM (P < 0.01) in the female SDR. Plasma phospholipids were raised up to 5.4 +/- 0.3 mM vs. 2.4 +/- 0.1 mM (P < 0.01). NAR have increased concentrations of plasma apolipoproteins A-1 (about 3-4-fold) and B (about 2-fold), but the levels of apolipoproteins A-IV and E are not increased. There was less proteinuria in the male NAR than in the male SDR (P < 0.01). Relevant histopathological findings in the NAR included hepatocytic lipofuscinosis and hemosiderosis in Kupffer cells. Tubular lesions were more common in kidneys from NAR than from SDR, and included protein casts, cortical lipofuscinosis, proximal tubular hyperplasia and proliferative interstitial nephritis. Glomerular changes were similar in both strains. Calcinosis of the aortic media and the corticomedullary region of the kidney was characteristically present in the female SDR but absent in the female NAR. Atherosclerotic lesions were not observed. In summary, 1-year-old NAR maintained on standard rat chow, are hyperlipoproteinemic. The increased levels of plasma LDL and HDL cholesterol are not associated with an increase in the incidence or severity of atherosclerotic or glomerular lesions.