[The role of proteolytic processes in the stimulation of lipolysis in the adipose tissue by somatotropin, adrenocorticotropin and beta-lipotropin].

The influence of proteinase inhibitors on the lipotropic effect of somatotropic (STH), adrenocorticotropic (ACTH) and beta-lipotropic (LPH) hormones in adipose tissue was studied in vitro. The effect of STH was found to be completely dependent on the activity of tissue serine proteinases of trypsin and chymotrypsin types. The effect of LPH partly depended on serine proteinases of chymotrypsin type, whereas that of ACTH--on chymotrypsin and carboxylic proteinases. The effects of all the three hormones were also manifested during lysosomal proteolysis. The protease-dependent inhibition was specific for polypeptide hormones and was unobserved in the lipotropic effect of adrenaline. The inhibiting effect of serine proteinase inhibitors on hormones pretreated with blood plasma or proteinases was much weaker than on untreated hormones. In adipose tissue the early insulin-like effect of STH, unlike the late lipotropic effect, was independent of proteolysis. It was assumed that primary proteolysis plays a role in the activation of polypeptide hormones which is necessary for the manifestation of the lipotropic action.