Determination of rat leptin activity in vitro using a novel luciferase reporter assay

Leptin is small cytokine-like protein that is involved in appetite and body weight regulation. Due to increased interest in using leptin as an anti-ob esity reagent, recombinant forms of leptin have been produced for several s pecies, including humans, mice, rats, pigs, dogs, sheep etc. The biological activities of such recombinant proteins were determined using various in v itro or in vivo systems; however so far, no specific assay system for rat l eptin is available. Since rats are representative animal models in obesity research, the establishment of a biological assay system for determining ra t leptin activity has been eagerly awaited. This study describes the genera tion of such a system using chinese hamster ovary (CHO)-cells that were tra nsfected with the long form of the rat leptin receptor isoform, OB-Rb, wher eby a signal transduces and activators of transcription-sensitive luciferas e reporter system is further employed to quantify the leptin-mediated signa ls. This system is the first rat-specific leptin bioassay system that has b een reported. It is expected that this assay will be used to further quanti fy and determine leptin activity from various biological fluids and sources .