Resistin concentrations in murine adipose tissue and serum measured by a new enzyme immunoassay

Objective: In an attempt to clarify the conflicting data on resistin mRNA expression and protein analysis by western blotting in adipose tissue and serum, we developed a sensitive enzyme‐linked immunosorbent assay (ELISA) for direct measurement of mouse resistin. Research Methods and Procedures: We developed polyclonal antibodies directed to the N (21 to 40) and C (79 to 91) termini of mouse resistin. Then, affinity‐purified anti‐C‐terminal resistin immunoglobin G (IgG) was biotinylated. ELISA was based on the sandwiching of antigen between antibody IgG coated on polystyrene plates and biotinylated antibody IgG. The bound biotinylated antibody was quantified with streptavidin‐linked horseradish peroxidase. Results: New ELISA can measure a concentration as low as 0.5 ng/mL of recombinant mouse resistin and is sensitive and specific enough to measure resistin protein in various adipose tissues and in sera. In normal mice, decreases in resistin concentrations in both white adipose tissue and serum were age dependent during 6 to 24 weeks of development. Resistin concentrations were significantly higher in omental adipose tissue in comparison with perirenal and abdominal adipose tissues and were 2‐ to 5‐fold higher in females than males during the growth period. ob/ob mice had significantly lower resistin concentrations than the control mice in both sera and the white adipose tissues, particularly in the omental fat. The treatment by testosterone, but not progesterone or β‐estradiol, in cultured adipocytes reduces resistin protein levels in a dose‐dependent manner. Discussion: New sensitive ELISA for mouse resistin clarified that the resistin concentrations in normal mice were markedly elevated in the omental adipose depots as compared with the perirenal and abdominal adipocyte depots and significantly elevated compared with adipose tissues in genetically obese mice.