Lipoprotein content and composition were studied in
ascites fluid of
puromycin aminonucleoside-nephrotic rats. All of the
lipoprotein density classes were found in
ascites fluid.
Protein levels compared to plasma were:
very low density lipoprotein (VLDL, d less than 1.006), 1.2%;
intermediate density lipoprotein (IDL, 1.006 less than d less than 1.02), 2.6%;
low density lipoprotein (
LDL, 1.02 less than d less than 1.063), 1.0%; and
high density lipoprotein (HDL, 1.063 less than d less than 1.21), 1.1%. The predominant
protein in
ascites fluid was
albumin, present at 1.9% of the plasma level. Radioiodinated VLDL and HDL injected intravenously into nephrotic rats appeared in
lipoprotein fractions of the
ascites fluid. VLDL and IDL
triacylglycerol content and particle diameter were low compared with plasma particles, suggesting peritoneal
triacylglycerol lipase activity; such
lipase activity could account for the increased proportion of
LDL in the
ascites fluid.
Ascites fluid
LDL and HDL
phospholipid and free
cholesterol were high and
cholesteryl ester was low.
Ascites lipoproteins contained the same
apolipoproteins as plasma, but in different proportions.
Ascites VLDL had higher
apolipoprotein B and lower
apolipoprotein E, while
LDL and HDL had higher
apolipoprotein E.
Ascites HDL could be separated by
heparin-Sepharose affinity column chromatography into a retained and a non-retained fraction, while nearly all nephrotic plasma HDL was non-retained. These data suggest that modification of
ascites fluid
lipoproteins occurs prior to their entry into the lymph and return to the blood, perhaps mediated by peritoneal macrophages.