Effect of simian virus 40 subcutaneous tumors on circulating lipids and lipoproteins in the Syrian hamster.

Circulating lipid levels and lipoprotein patterns in the Syrian hamster were determined at various times after subcutaneous inoculation with simian virus 40 (SV40) strain F, strain A-2895, or Fortner melanoma tumor cells. SV40 F tumors induced a rapid triphasic elevation of serum total lipids through inhibition of prebeta lipoprotein catabolism. Alpha lipoprotein levels declined in proportion to tumor mass. Liver wet weight and total lipid content increased significantly, but a normal rate of 3H-glycerol incorporation into polyanion precipitable (prebeta) serum lipoprotein was maintained. Determination of serum endogenous lipase, lecithin:cholesterol acyltransferase (LCAT), and cholinesterase activities indicated that these enzymes were not primarily responsible for the tumor-induced hyperlipidemia. Tumor-bearing animals also had selectively increased rates of protein and lipid excretion into the urine, with no evidence of gross hepatocellular or kidney damage. Growth of SV40 A-2895 tumors in hamsters resulted in a large increase in the rate of prebeta lipoprotein synthesis and degradation. Circulating prebeta lipoprotein levels were elevated much later in these animals, subsequent to a marked decrease in LCAT activity. Quite different results were obtained with Fortner melanoma, even large tumors having only a moderate effect on serum total lipid levels and lipoprotein patterns in the Syrian hamster.