Tissue Specific Fatty Acid Uptake
Tissue fatty acid uptake is assessed by measuring tissue-specific incorporation of circulating 125I-BMIPP (Rottman et al. Am. J. Physiol. 2002). The beta-methyl modification of the long-chain fatty acid BMIPP (beta-methyl-p-iodophenylpentadecanoic acid) causes terminal trapping in the TCA cycle. Studies in man and a variety of small animal models, including rodents, have shown that BMIPP uptake and metabolism closely tracks that of endogenous long-chain fatty acids in a variety of normal and pathophysiologic states.
BMIPP is dissolved in proprionic acid, and incorporation of 125I is catalyzed with CuSO4. After extraction, the purified 125I-BMIPP is dissolved in ursodeoxycholic acid, filtered, and adjusted to defined activity. This stable compound is suitable for direct intravascular injection. Serum levels are stable in tracer amounts after injection, and tissue incorporation is measured by gamma counting of freeze-clamped samples in protocols compatible with the simultaneous assay of, for example, [2-3H]DG.