COMPARISON OF 2 METHODS TO ASSESS THE TISSUE BLOOD PARTITION-COEFFICIENT FOR XENON IN SUBCUTANEOUS ADIPOSE-TISSUE IN MAN

A new method to calculate the tissue/blood partition coefficient (lamb da) for xenon in studies on the subcutaneous adipose tissue blood flow was compared with a previously reported method based on local skinfol d thickness (lambda(LST)). The former method included needle biopsies from the abdominal and femoral subcutaneous adipose tissue, and the me an fat cell diameter was measured (lambda(ECT)). The extracellular tis sue fraction in subcutaneous tissue was then estimated from a diagram. The tissue lipid content was approximated to equal the relative intra cellular volume and Ostwald's solubility coefficients for Xe-133, base d on the distribution of xenon in lipid, albumin and 0.9% saline were applied. Estimated lambda-values based on needle biopsies from the abd ominal site were: 8.6+/-0.1 versus 9.9+/-0.4 ml g(-1) (mean+/-SE) (P<0 .05) and from the femoral site: 9.1+/-0.1 versus 9.6+/0.2 in lean (n=1 0) and obese subjects (n=10), respectively. The corresponding lambda-v alues obtained from skinfold measurements were: 6.2+/-0.5 versus 11.0/-0.4 (P<0.001) and 6.9+/-0.3 versus 11.4+/-0.4 (P<0.001) in lean and obese subjects, respec tively. Pooled lambda(LST)-values correlated po sitively with estimated adipose tissue blood flow (ATBF) (r:0.34, P<0. 05, n=40) whereas no such correlation was found for lambda(ECT)-values . In conclusion, a new method is presented which may allow an accurate determination of, and which may lead to reliable data on, subcutaneou s ATBF in both lean and obese subjects. Comparative studies indicate t hat the widely used lambda-value of 10.0 in subcutaneous adipose tissu e may be used as a rough estimate for subcutaneous blood flow studies in these patient groups.