ADIPOSE-TISSUE EXTRACTION OF CIRCULATING INSULIN IN ANESTHETIZED ZUCKER OBESE RATS

OBJECTIVE: To determine whether adipose tissue removes a significant p roportion of circulating insulin in the obese rat in vivo. DESIGN: Blo od samples were obtained from the carotid artery and the venous side o f hind leg muscle, epididymal fat pads and liver (portal and suprahepa tic veins), they were used for estimation of insulin disappearance acr oss the tissue. SUBJECTS; Anaesthetized Zucker lean (Fa/7) and obese ( fa/fa) adult male rats. MEASUREMENTS: Blood flow, glycaemia and insuli naemia. RESULTS: In lean rats, the liver accounted for practically all insulin extraction (498+/-149 fmol . s(-1)), removing more than half of the portal insulin in a single pass. In the obese rats, the liver e xtracted a similar amount in absolute terms (397+/-108 fmol . s(-1)), representing only 16% of portal insulin. In the hind leg muscle of bot h groups and in the adipose tissue of lean rats, insulin balances were not different from zero; but in obese rats, adipose tissue extracted a similar amount of insulin (405+/-127 fmol . s(-1)) to that removed b y the liver. CONCLUSIONS: In the Zucker obese rat, peripheral adipose tissue removes as much insulin from the blood as the liver does, in co ntrast with lean rats, in which the latter is responsible for practica lly all insulin extraction.