Lipid interference with fluorometric assay of DNA in adipose tissues under various conditions

Interference by lipids with fluorometric assay of DNA in adipose tissues using Hoechst 33258 was investigated. Mixed glycerides shifted the emission maximum of standard DNA and induced a dose-dependent increase in fluorescence intensity. Glycerides in the samples containing a known concentration of DNA yielded erroneously higher DNA concentrations. The DNA concentrations obtained from acetone-defatted white and brown adipose tissues (WAT and BAT) were lower than those of non-defatted ones, while DNA content did not differ in low lipid-containing skeletal muscle between defatted and non-defatted samples, indicating that large amounts of lipids interfere with DNA measurement using Hoechst 33258 and that acetone defatting is a simple method to avoid this interference. Using this defatting method, the cellularity of WAT and BAT was estimated in rats under various experimental conditions. Cold-acclimation and repetitive immobilization stress decreased the body weight gain and the epididymal WAT weight. Sucrose overfeeding increased WAT weight but not body weight. These treatments of 4 weeks' duration did not induce any significant difference in WAT cell number from controls, while cold-acclimation increased the tissue cell number as well as the BAT weight.