CONTRIBUTIONS OF LIVER AND KIDNEYS TO GLYCEROL PRODUCTION AND UTILIZATION IN THE DOG

The classical concept holds that liver and kidneys are the main sinks of glycerol released by adipose tissue. However, rates of glycerol app earance (R(a)) exceed the rate of glycerol delivery to liver and kidne ys. We measured the hepatic and renal contributions to glycerol produc tion and utilization in anesthetized dogs that were fasted either over night or for 24 h after 3 days on a carbohydrate-free diet. Dogs were infused with [H-2(5)]glycerol, and the concentration and H-2 enrichmen t of glycerol were measured across liver and kidney. After a baseline period, either norepinephrine or glucose plus insulin was infused to a lter the rate of glycerol production. Our study shows that the product ion of glycerol by liver and kidneys amounted to 4-9% and 4-7% of the R(a) of glycerol, respectively. Uptake of glycerol by liver and kidney s amounted to 26-30 and 10-19% of the R(a) of glycerol, respectively. Thus, contrary to the classical concept, the bulk of glycerol utilizat ion occurs in nonhepatic, nonrenal tissues that have very low glycerol kinase activity per gram.