Measurement of Total Body Fat in Living Rats by Absorption of Cyclopropane

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Abstract
Total body fat of rats was detd. in vivo by measurement of the quantity of cyclopropane absorbed by the animal at a known tension of the gas. A measured quantity of cyclopropane was admd. to each animal in an enclosed gas chamber of known volume. The tissues of the rat come into equilibrium with cyclopropane at the tension of the gas existing in the chamber in 90-150 min.: From the solubility coefficients of cyclopropane in fat and non-lipid tissues and the concn. of cyclopropane in the chamber at equilibrium, the fat content of the rat was calculated. Due to its extremely high fat:water solubility ratio (approx. 52:1), about 90% of all cyclopropane in the body is present in fat once equilibrium occurs. Values for total body fat by this method approx. the wt. of total ether extractable material closely. Mean wt. of fat of 10 white rats by cyclopropane absorption was 40.4 g., by ether extraction 40.1 g. The avg. deviation was t 2.1 g. The avg. fat content by both methods was 13.2% of the body wt., with an avg. deviation of + 0.7%.