THE SOURCE OF ENDOGENOUS LIPID IN THE THORACIC DUCT LYMPH OF FASTING RATS

¹ Department of Physiology, The University of Western Australia, Nedlands

The output of esterified fatty acid in the thoracic duct lymph of fasting, unanæsthetized rats decreased by 80 per cent when a bile fistula was produced. Steady infusion of sodium taurocholate, 5 or 10 mg./hr. in saline, did not reverse this fall. This suggested that it was the loss of biliary lipids and not primarily that of bile salts which was responsible for the decreased lymph lipid. The output of esterified fatty acid in bile of rats with chronic bile fistulae was small. However, experiments in which bile was returned by re-entrant cannula and sampled only for short periods showed that operation depressed biliary lipid output for about 24 hr. and drainage of bile clearly decreased biliary lipids within 2-4 hr. In each of a group of rats with re-entrant biliary cannulae the output of biliary lipids in the first 2 hr. of drainage was more than enough to account for the decrease in output of esterified fatty acid in fasting lymph in each rat after continuous biliary drainage was established. Gas liquid chromatography showed that before biliary drainage was established, fasting lymph lipids were rich in fatty acids characteristic of bile but after biliary drainage the fatty acid pattern closely resembled that of plasma. It is suggested that fatty acid liberated from phospholipids of bile in the intestinal lumen contribute a major portion of the esterified fatty acid of fasting lymph and that lipoproteins passing from plasma into lymph provide much of the remainder. The prompt effect of biliary drainage on phospholipid output in bile is briefly discussed.

Note:

This work was carried out with the aid of grants from National Health and Medical Research Council of Australia, the Medical Research Grants Committee, The University of Western Australia and Colombo Plan.