Variables of myocardial backdiffusion, determined with 17-IODO-131 heptadecanoic acid in the normal dog heart

Abstract

Under normal and ischemic conditions backdiffusion of radiolabeled non-esterified fatty acids (NEFA) has been demonstrated. In the fasted normal canine heart the extraction fraction (EF) during interventions with glucose or lactate loading, vasodilation, and metabolic level augmentation was determined, and compared with the control EF. Backdiffusion alterations were deduced from the EF changes. After iv injection of 17-iodo-131 heptadecanoic acid (IHDA), 11 blood samples were drawn from aorta and coronary sinus in a time period of 60 minutes. In the control and vasodilation group the EF slowly decreased from 40 to 10%. In contrast, the EF in the noradrenaline group was constant. During glucose and lactate infusion the EF became negative within 10 min and remained negative. These results suggest that during physiological circumstances backdiffusion is determined by the metabolic level of the heart and its substrate availability.

The Influence of Lactate and Dipyridamole on Myocardial Fatty Acid Metabolism in Man, Traced with 123l-17-lodo-heptadecanoic Acid

“…The reduced uptake observed in the present study may be interpreted as a result of acyl-CoA synthetase inhibition. An increased myocardial backdiffusion of radioiodinated fatty acids, determined in the canine coronary sinus after lactate loading, is in line with this explanation (12).…”

Interrelationship between lactate and cardiac fatty acid metabolism

“…1) is impaired and part of fatty acyl-CoA is used for triacylglycerol formation. In addition to incorporation into the triacylglycerol pool, in dogs with high levels of circulating lactate part of fatty acids extracted by the heart was found to return to the extracellular space [16,25]. Additional evidence for a crucial role of a carnitine related step in lactate-induced inhibition of fatty acid oxidation is the fact that the oxidation of octanoate, a fatty acid that does not require carnitine for entry into mitochondria, is insensitive to high levels of circulating lactate [17,24].…”

Role of Fatty Acid Imaging with 123I- β-methyl-p-123I- Iodophenyl-Pentadecanoic Acid (123I-BMIPP) in Ischemic Heart Diseases

“…In the first step of the common pathway of fatty acid metabolism, BMIPP also underwent ATP dependent conversion to BMIPP-CoA. Once BMIPP-CoA is synthesized, it is hardly back-diffused out of the cell and is retained within it [39,40]. Therefore, BMIPP myocardial retention may relate to the ATP level of the cells.…”