Ga. Kaysen et al., EFFECT OF PLASMA ONCOTIC PRESSURE ON APOLIPOPROTEIN LEVELS IN RATS WITH HEYMANN NEPHRITIS, Mineral and electrolyte metabolism, 22(1-3), 1996, pp. 31-38
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 apolip
oprotein (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 n above 20 mm Hg. Either saline or a mixture of amino acids c
alculated 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 ap
o A-I, and apo E levels in HN even though proteinuria continued unabat
ed, In contrast, apo B remained significantly elevated in HN infused w
ith albumin, but was reduced to normal by ficoll, Fifteen non-nephroti
c control animals were studied in 3 groups of 5 animals each; one rece
iving human albumin, one ficoll, both adjusted to increase plasma pi t
o supranormal levels, and a 3rd group received saline. Ln contrast to
HN, plasma apo A-I, E, and B levels were unaffected by albumin or fico
ll infusion in control animals, Ficoll caused a significant reduction
in apo A-IV in both HN and control animals to subnormal levels, but al
bumin 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 do
es not increase plasma apo A-I or E levels, Factors other than albumin
concentration or pi, such as persistent urinary protein loss, play a
role in establishing increased apo B containing lipoproteins in the ne
phrotic syndrome, Ficoll may cause changes in plasma lipoprotein level
s by means other than its ability to increase plasma pi.