Extraction of long-chain fatty acids in isolated rat heart during acute low-flow ischemia.
Although beta-oxidation of fatty acids is suppressed rapidly during ischemia, the behavior of fatty acid extraction at different flow rates is incompletely understood. This study assessed the relationship between flow and extraction of (123)I-iodophenylpentadecanoic acid (IPPA) in the isolated heart model, especially at low flow.


METHODS
Isolated hearts from male Wistar rats (n = 15) were subjected to retrograde perfusion with constant flow (Krebs Henseleit solution containing 10 mmol/L glucose). A latex balloon in the left ventricle allowed isovolumetric contractions and ventricular pressure measurements. The extraction of (123)I-IPPA was assessed with the indicator dilution technique and (99m)Tc-albumin as the intravascular reference. The flow was either increased from the control flow (8 mL/min) until 300% or reduced until 10%. (123)I-IPPA extraction was measured three times before and 10 min after flow alteration. The tracer uptake was estimated from the product of net extraction and flow.


RESULTS
The mean (123)I-IPPA extraction at the control flow (third measurement) was 51.6% +/- 2.8%. Between flow rates of approximately 25% and 300%, (123)I-IPPA extraction increased exponentially at decreasing flow rates. At flow rates < or =25% of the control flow, (123)I-IPPA extraction was exponentially higher than predicted. (123)I-IPPA uptake and flow changed largely in parallel. During low flow, the rate-pressure product showed the expected decline (perfusion-contraction matching).


CONCLUSIONS
The extraction of (123)I-IPPA is preserved and slightly increased (relative to flow) during acute low-flow ischemia.
Richter
W S
WS
Clinic for Nuclear Medicine, University Hospital Charité, Humboldt University of Berlin, Berlin, Germany.
Fischer
S
S
Ernst
N
N
Munz
D L
DL
D000818:Animals; D001783:Blood Flow Velocity; D003326:Coronary Circulation; D005227:Fatty Acids / Q000378:metabolism*; D006321:Heart / Q000000981:diagnostic imaging; D066298:In Vitro Techniques; D007201:Indicator Dilution Techniques; D007457:Iodine Radioisotopes; D007462:Iodobenzenes / Q000493:pharmacokinetics; D008297:Male; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism*; D011877:Radionuclide Imaging; D051381:Rats; D017208:Rats, Wistar
D005227:Fatty Acids; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; C025391:omega-(4-iodophenyl)pentadecanoic acid