Abstract
1. When epididymal fat bodies from starved rats are incubated for 3.5hr. at 37 degrees in a defined medium in vitro the total clearing-factor lipase activity rises to approximately twice its initial value. 2. During the incubation period part of the tissue clearing-factor lipase activity appears in the medium. 3. Heparin, glucose, insulin, and HCO(3) (-) and K(+) ions are shown to be important medium constituents.