Local Factors Modulate Tissue-Specific NEFA Utilization Assessment in Rats Using 3H-(R)-2-Bromopalmitate

Insulin-resistant states are associated with accumulation of muscle lipid, suggesting an imbalance between lipid uptake and oxidation. We have employed a new fatty-acid tracer [9,10-3H]-(R)-2-bromopalmitate (3H-R-BrP) to study individual-tissue nonesterified fatty acid (NEFA) uptake in states with diminished or enhanced lipid oxi-dation. 3H-R-BrP was administered to conscious male Wistar rats (~300 g) during fasting (5, 18, or 36 h), acute blockade of -oxidation (etomoxir, 15 µmol/kg), and insulin infusion (0.25 U · kg–1 · h–1). Estimates of NEFA clearance rates (Kf*) and absolute rates of uptake (Rf*) were calculated from tissue accumulation of 3H-R-BrP products. In the basal state, NEFA uptake was dependent on the oxidative capacity of tissues: Rf * in brown adipose tissue (BAT)> heart (HRT)> diaphragm (DPHM)> re