A chicken leptin-specific radioimmunoassay

Recombinant chicken leptin was used to produce an antiserum in order to dev elop a specific and sensitive radioimmunoassay (RIA) for chicken leptin in plasma and serum. We have used either murine or chicken leptin as tracer an d competition curves were performed using recombinant chicken leptin. Varia tions in leptin plasma levels in different chicken strains and various nutr itional states were correlated with the physiological status. Leptin plasma concentrations were regulated by the nutritional state with higher levels in the fed state as compared to the fasted state (3.36 +/- 0.13 versus 2.78 +/- 0.11 ng/ml) and being dependent upon the age. Higher leptin levels wer e found in 22 week-old as compared to 15 week-old layer chickens (2.709 +/- 0.172 versus 1.478 +/- 0.102 ng/ml). We have also shown that the multispec ies leptin RIA kit (LINCO Inc.) underestimated leptinemia compared to the c hicken leptin- specific RIA reported here. In conclusion the RIA developed in the present study is specific to the chicken and thus may be considered as powerful tool for investigating the physiological significance of leptin in chickens. (C) 2000 Elsevier Science Inc. All rights reserved.