Fatty acid binding protein in heart and skeletal muscles of the migratory barnacle goose throughout development

The long-distance migratory flights of birds are predominantly fueled by th e oxidation of fatty acids, which are sourced primarily from extracellular adipose stores. These fatty acids have to be transported, via the circulato ry system, to the mitochondria of the active muscles. An important facilita tor of fatty acid transport within the cytoplasm of muscle cells is fatty a cid binding protein (FABP), which serves as an intracellular carrier of lon g-chain fatty acids. In mammals, the muscular FABP content is related to th e fatty acid oxidation capacity of the tissue. The aim of this study was to measure FABP in samples taken from the cardiac, pectoralis, and semimembra nosus muscles of a long-distance avian migrant, the barnacle goose (Branta leucopsis), at various stages of development. Western blot analysis identif ied a single goose muscle protein of 15 kDa that was able to bind fatty aci ds and showed a 66% cross-reactivity with antibodies against human heart-ty pe FABP. Captive goslings showed no significant changes in FABP content of either the heart (62.6 +/- 10.6 mu g/g wet wt) or the semimembranosus muscl e (8.4 +/- 1.9 mu g/g wet wt) during development. However, in both peripher al and deep sites within the pectoralis muscle, FABP content of samples tak en from captive goslings were similar to 10-fold higher throughout developm ent and reached values of 30-40 mu g/g wet wt in fledging goslings at 7 wk of age. A further twofold higher value was seen in wild but not in captive goslings immediately before migration (12 wk of age). Similarly, FABP conte nt was significantly higher in pectoralis samples taken from wild adults (9 4.3 +/- 3.6 mu g wet wt) compared with those from captive adults (60.5 +/- 3.6 mu g/g wet wt). These results suggest that the experience of flight act ivity may be of critical importance in achieving maximal expression of FABP in the pectoralis muscles of postfledging and mature geese immediately bef ore migration.