The
obese (ob) gene has recently been isolated by positional genetics, the mutation of which causes marked obesity and diabetes in mice. In the present study, we elucidated the tissue distribution of the
ob gene expression in rats and examined the gene expression in genetically obese-hyperglycemic Wistar fatty rats. Northern blot analysis using the rat
ob cDNA probe identified a single mRNA species of 4.5 kilobase in size in the adipose tissue, while no significant amount of
ob mRNA was detected in other tissues in Sprague-Dawley and Wistar rats. The
ob gene expression occurred in the adipose tissue with region-specificities. The rank order of the
ob mRNA level in the adipose tissue was epididymal, retroperitoneal, and pericardial white adipose tissue > mesenteric and subcutaneous white adipose tissue ≥ interscapular brown adipose tissue in both rat strains. Furthermore, expression of the
ob gene was augmented in all the adipose tissue examined in Wistar fatty rats at the stage of established obesity.
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