title: Effect of plasma oncotic pressure on apolipoprotein levels in rats with Heymann nephritis.
abstract: The nephrotic syndrome is characterized by reduced plasma albumin and colloid osmotic pressure (pi). Infusion of dextran or albumin reduces lipid levels suggesting that reduced plasma pi plays a role in causing hyperlipidemia in the nephrotic syndrome. To determine whether apolipoprotein (Apo) levels were affected by pi, passive Heymann nephritis (HN) was created in 20 rats. Hyperoncotic (25%) human albumin or ficoll was infused continuously into each of 5 HN rats adjusted to maintain a plasma pi above 20 mm Hg. Either saline or a mixture of amino acids calculated to approximate those released from catabolized human albumin were infused into 5 HN as controls. Urinary rat albumin loss was not different between the 4 groups of HN. Plasma apo A-I, B and E were all increased significantly in saline and amino acid infused HN, but apo A-IV was decreased. Infusion of either albumin or ficoll normalized apo A-I, and apo E levels in HN even though proteinuria continued unabated. In contrast, apo B remained significantly elevated in HN infused with albumin, but was reduced to normal by ficoll. Fifteen non-nephrotic control animals were studied in 3 groups of 5 animals each; one receiving human albumin, one ficoll, both adjusted to increase plasma pi to supranormal levels, and a 3rd group received saline. In contrast to HN, plasma apo A-I, E, and B levels were unaffected by albumin or ficoll infusion in control animals. Ficoll caused a significant reduction in apo A-IV in both HN and control animals to subnormal levels, but albumin infusion was without effect. Reduced plasma pi, but not reduced plasma albumin is necessary for increased apo A-I, and E levels in the nephrotic syndrome. When plasma pi is normal extensive proteinuria does not increase plasma apo A-I or E levels. Factors other than an albumin concentration or pi, such as persistent urinary protein loss, play a role in establishing increased apo B containing lipoproteins in the nephrotic syndrome. Ficoll may cause changes in plasma lipoprotein levels by means other than its ability to increase plasma pi.
authors.affiliation: Department of Medicine, University of California Davis, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Kaysen
authors.forename: H
authors.initials: H
authors.lastname: Jones
authors.forename: J A
authors.initials: JA
authors.lastname: Joles
authors.forename: A
authors.initials: A
authors.lastname: van Tol
mesh_terms: D000818:Animals; D016632:Apolipoprotein A-I / Q000097:blood; D001053:Apolipoproteins / Q000097:blood*; D001054:Apolipoproteins A / Q000097:blood; D001055:Apolipoproteins B / Q000097:blood; D001057:Apolipoproteins E / Q000097:blood; D002784:Cholesterol / Q000097:blood; D003102:Colloids / Q000032:analysis; D005362:Ficoll / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D005921:Glomerulonephritis / Q000097:blood*; D006801:Humans; D007262:Infusions, Intravenous; D009997:Osmotic Pressure; D010710:Phosphates / Q000097:blood; D051381:Rats; D012709:Serum Albumin / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D014280:Triglycerides / Q000097:blood
chemical_list: D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D001054:Apolipoproteins A; D001055:Apolipoproteins B; D001057:Apolipoproteins E; D003102:Colloids; D010710:Phosphates; D012709:Serum Albumin; D014280:Triglycerides; C022205:apolipoprotein A-IV; D005362:Ficoll; D002784:Cholesterol