CHOLINESTERASE OF ADIPOSE TISSUE

¹ The Wellcome Research Laboratories, Tuckahoe, New York

Adipose tissue of the rat, mouse, rabbit, guinea pig and cat contains an enzyme which catalyzes in vitro the hydrolysis of acetylthiocholine (ATCh). The esterase activity of rat epididymal or perirenal adipose tissue is less than that of brain and heart but greater than that of blood, liver or kidney when enzyme activity is compared on the basis of wet weight of tissue. The hydrolysis of ATCh by the enzyme of rat epididymal adipose tissue is inhibited by 1 x 10^-5 M neostigmine and by DFP and Ro2-0683 which are antagonists of nonspecific ChE. The acetylcholinesterase inhibitors, B. W. 284C51 and B. W. 62C47, inhibit the enzyme slightly. Propionylthiocholine is hydrolyzed more rapidly than ATCh and butyrylthiocholine is metabolized less rapidly. Differential centrifugation experiments indicate that most of the esterase of rat epididymal adipose tissue is located in the microsomal fraction. The enzyme activity of adipose tissue is increased significantly by freezing or by homogenizing with a high speed tissue grinder. The cause of the increase of enzyme activity is not known.