Clearing-factor lipase in adipose tissue. Factors influencing the increase in enzyme activity produced on incubation of tissue from starved rats in vitro.

1. Evidence is presented that the increase in clearing-factor lipase activity that occurs when adipose tissue from starved rats is incubated in a defined medium in vitro is due to an increase in the total enzyme content of the system. It is shown that the clearing-factor lipase activity rises to reach a plateau level where, it is suggested, rates of enzyme synthesis and of enzyme destruction become balanced. 2. The presence of heparin in the incubation medium results in the extraction of part of the clearing-factor lipase originally present in the adipose tissue and this could provide the stimulus for the increase in total enzyme content. 3. Glucose is required in the incubation medium at a very low concentration. It can be replaced by fructose, but not by pyruvic acid, lactic acid, glyceric acid or dihydroxyacetone. 4. Adrenaline and corticotrophin inhibit the increase in enzyme activity when they are present in the incubation medium. 5. The high clearing-factor lipase activity associated with adipose tissue of fed rats is decreased by 50% within 3hr. of the injection of puromycin.