Role of cardiac lymph and interstitial fluid in lipid metabolism of canine heart.

To determine whether cardiac interstitial spaces participate in cardiac fatty acid pool, the relationship between cardiac lymph and arterial plasma free palmitate and triglycerides was studied in anesthetized dogs [14C]Sucrose, infused at a constant rate in a femoral vein, appeared in the lymph at 90% of its arterial concentration within 60 min. On the other hand, when [1-14C]palmitate was infused at the same rate and at the same site, the ratio of lymph to arterial plasma 14C-labelled free fatty acids (FFA) was only 21% at 60 min and 25% at 120 min, even though the concentrations of endogenous FFA in lymph and arterial plasma were the same. The ratio reached 90% only 24 h after a bolus injection of [3H]palmitate. [1-14C]Palmitate in the lymph triglyceride fraction was only 8% of that in plasma. Although the lymph composition may be influenced by the metabolism of heart muscle, cardiac adipose tissue, and serum lipoproteins, these results indicate the presence of a pool of myocardial fatty acids which may be partly located in the interstitial spaces.