LIPID INTERFERENCE WITH FLUOROMETRIC ASSAY OF DNA IN ADIPOSE TISSUES UNDER VARIOUS CONDITIONS

Interference by lipids with fluorometric assay of DNA in adipose tissu es 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 kno wn 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 o nes, while DNA content did not differ in low lipid-containing skeletal muscle between defatted and non-defatted samples, indicating that lar ge amounts of lipids interfere with DNA measurement using Hoechst 3325 8 and that acetone defatting is a simple method to avoid this interfer ence. Using this defatting method, the cellularity of WAT and BAT was estimated in rats under various experimental conditions. Cold-acclimat ion and repetitive immobilization stress decreased the body weight gai n and the epididymal WAT weight. Sucrose overfeeding increased WAT wei ght but not body weight. These treatments of 4 weeks' duration did not induce any significant difference in WAT cell number from controls, w hile cold-acclimation increased the tissue cell number as well as the BAT weight.