Lipolytic activity in rat epididymal fat pads

Abstract

Rat epididymal fat pads were incubated in the presence of heparin and epinephrine. The lipase activity present in the incubation medium and in the tissue after homogenization was measured, partially purified, and characterized. A lipase was eluted into the incubation medium which was considered to be identical with lipoprotein lipase described by E. D. Korn. It had a pH optimum of 8.5, required serum proteins and ammonium sulfate as cofactors, and was inhibited by high ionic strength, protamine sulfate, EDTA, and deoxycholate. The yield of this lipase was greater when heparin was present in the incubation medium and when the pads were obtained from fed rather than fasting rats. This lipase was also present in the tissue homogenates. A lipase differing from lipoprotein lipase was found in the tissue homogenates. It had a pH optimum between 6.5 and 7 and required albumin for optimal activity. It was inhibited by NaF. The yield of this lipase was greatest in the homogenates of fat pads obtained from fasting rats and incubated with epinephrine. Position-specificity tests utilizing a pure triglyceride of known fatty acid composition indicated preferential alpha fatty acid hydrolysis by both lipases as well as by pancreatic lipase.