1. The mechanism whereby p-chlorophenoxyisobutyrate (CPIB) lowers plasma non-esterified fatty acid concentrations has been studied in dogs by measuring the associated changes in adipose tissue metabolism.
2. CPIB lowered arterial concentrations of non-esterified fatty acids during isoprenaline infusion by a mean value of 41%.
3. This was accompanied by a proportionate decrease (45%) in the release of non-esterified fatty acids from subcutaneous adipose tissue in situ, and by a lesser reduction (22%) in that of glycerol.
4. Adipose tissue blood flow was unchanged by CPIB.
5. These findings indicate that the lowering effect of CPIB on non-esterified fatty acid concentrations derives principally from decreased mobilization rather than from increased tissue uptake of the fatty acids, and that this reflects both inhibited lipolysis and enhanced re-esterification of the fatty acids in adipose tissue.