WHOLE-BODY COMPOSITION OF RATS DETERMINED BY DUAL-ENERGY X-RAY ABSORPTIOMETRY IS CORRELATED WITH CHEMICAL-ANALYSIS

The use of dual energy X-ray absorptiometry (DXA) is increasing in ani mal research, but data comparing whole body composition by DX4 and che mical analysis (CHEM) in rats are limited, Lean and obese Zucker femal e rats were used to compare DXA (QDR1000W, Hologic, Waltham, MA) value s with CHEM data for percent fat (%FAT(DXA), %FAT(CHEM)), jean body ma ss (%PROTDXA, %PROTCHEM) and bone mineral content (%BMCDXA, %ASH(CHEM) ) Four groups of rats (n = 9) were tested for differences in body comp osition due to consumption of a 100 g guar gum supplement/kg to see if DXA was as sensitive as CHEM in detecting body composition difference s induced by diet, The study was analyzed using a split-plot ANOVA whe re the main plot was a 2 x 2 factorial with phenotype (obese or lean) and treatment (guar gum or control) as the effects, and the subplot wa s method of detecting body composition (DXA and CHEM), which was treat ed as a repeated measure, Absolute values for percent fat differed sig nificantly (P < 0.0001) between the two methods as %FAT(DXA) was consi stently higher than %FAT(CHEM). There was not a statistically signific ant difference due to method for %PROT (P = 0.13), Values for %BMCDXA were significantly (P < 0.0049) lower than %ASH(CHEM) values, The diff erences in body composition due to diet treatment were detected simila rly by DXA and CHEM, Significant correlations were found between the m ethods (P < 0.0001) for %FAT (r = 0.99), %PROT (r = 0.96) and %BMC or ASH (r = 0.81), Bland-Altman plots showed good agreement between metho ds, and regression equations were developed to estimate CHEM values fr om DXA readings. DXA, may provide an alternative method for assessing changes in whole body composition.