Fatty acid metabolism via triglyceride in the salmon heart.

The composition of heart lipids was analyzed and the metabolism of heart triglycerides investigated in pre- and post-spawning pink salmon (Oncorhyncus gorbuscha). Comparison of the two kinds of fish indicated that the latter have smaller hearts containing less total lipid. The most notable finding involved virtually complete loss, on average 94%, of heart triglycerides during the fresh water migration to the spawning grounds. In vivo palmitate-1-¹⁴C incorporation into heart triglycerides, as well as heart slice incubations, revealed the triglyceride pathway as an active metabolic route even in post-spawning fish that were only hours from death. The heart took up and retained fatty acid from the serum more readily than liver, skeletal muscle or brain. Following intravenous injection of the label, maximum specific activity of heart triglycerides was achieved in approximately one hour. The rapid turnover of the glyceride pool coupled with its diminishing mass is evidence of a substantial fatty acid flow through this intermediate in the heart muscle.