Demonstration of hepatic triglyceride lipase-like activity in ascites fluid of mice with sarcoma 180.

The contents of apolipoproteins of plasma and ascites fluid of mice with Sarcoma 180 were measured. The apolipoprotein A-I contents of plasma decreased with development of the tumor. The apolipoprotein C-II and C-III contents of plasma reached a maximum on day 7 after tumor inoculation and then decreased. The apolipoprotein A-I content of the ascites fluid was lower than that of normal mouse plasma. In contrast, the apolipoprotein C-II and C-III contents of the ascites fluid were higher than those of normal mouse plasma. The ascites fluid of mice with Sarcoma 180 was found to contain at least two lipases. One had a pH optimum of 5.5-7.0 and was strongly inhibited by chlorpromazine. The other had an alkaline pH optimum and was inhibited only slightly by chlorpromazine. When the ascites fluid was applied to a heparin-Sepharose column 40-45% of the applied triglyceride lipase activity was retained on the column, which was eluted with 0.75 M NaCl. This fraction was inhibited by heat-inactivated (56 degrees C, 10 min) human serum, and was relatively resistant to l M NaCl. These results suggest that one of the lipolytic enzymes present in the ascites fluid of mice with Sarcoma 180 is hepatic triglyceride lipase.