Tissue lipoprotein lipase,serum, and urinary lipids and lipoproteins in experimental glomerulonephritis of rats (Heymann's nephritis)

Serum and urinary cholesterol, triglycerides, high-density lipoproteins, and tissue lipoprotein lipase levels were measured in a group of rats in which experimental glomerulonephritis (EGN) was induced by an injection of renal tubular antigen in Freund's complete adjuvant. Progressively increasing proteinuria beginning after approximately the eighth week was associated with a progressive increase in the levels of serum cholesterol, triglycerides, and high-density lipoprotein cholesterol. Significant lipiduria occurred at the ninth week. Lipoprotein electrophoresis of concentrated urine showed the presence of a band with alpha lipoprotein (high-density lipoprotein) mobility. Eleven weeks after disease induction, the rats were killed and the tissue levels of lipoprotein lipase were measured. A homogenized preparation of the heart, liver, adipose tissue, and skeletal muscle using [¹⁴C]triolein as substrate was used. Nephrotic rats had less than half the myocardial lipoprotein lipase levels of controls (2099 ± 420 and 962 ± 142 (mean ± SD) nm free fatty acids/mg tissue/hr, respectively; P < 0.05). Hepatic, skeletal muscle, and adipose tissue lipoprotein lipase levels were not significantly different in the two groups of rats.These results document the potential usefulness of the rat (EGN) model for further studies in lipoprotein metabolism in nephrotic syndrome. The significance and pathogenesis of reduced myocardial lipoprotein lipase requires further investigation.