Effect of Plasma Oncotic Pressure on Apolipoprotein Levels in Rats with Heymann Nephritis

George Kaysen, Hardin Jones, Japp A. Joles, Arie Van Tol

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

The nephrotic syndrome is characterized by reduced plasma albumin and colloid osmotic pressure (π). Infusion of dextran or albumin reduces lipid levels suggesting that reduced plasma π plays a role in causing hyperlipidemia in the nephrotic syndrome. To determine whether apolipoprotein (Apo) levels were affected by π, 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 π 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 π 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 π, but not reduced plasma albumin is necessary for increased apo A-I, and E levels in the nephrotic syndrome. When plasma π is normal extensive proteinuria does not increase plasma apo A-I or E levels. Factors other than albumin concentration or π, 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 π.

Original languageEnglish (US)
Pages (from-to)31-38
Number of pages8
JournalMineral and Electrolyte Metabolism
Volume22
Issue number1-3
StatePublished - 1996

Keywords

  • Albumin
  • Albuminuria
  • Apo A-I
  • Apo A-IV
  • Apo B
  • Apo E
  • Lipids

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

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