[Structurally functional organization of corticotropin: lipolytic and steroidogenic activity of some of its fragments].

The influence of ACTH fragments, possessing structural elements, common for certain groups of peptide hormones and kinins--"common" fragments and cluster of basic amino-acids--(Lys 17,18-ACTH 11-18-NH2--I; ACTH 11-13-NH2--II; NH2CO-ACTH18-20-NH2--III) on lipolytic effect of ACTH in rat isolated fat cells and on the steroidogenic effect of ACTH in isolated rat adrenal cells was studied. Fragment I exerts a steroidogenic effect (alpha=0,84) at concentrations of 1--100 microng/ml. At low concentrations (10(-8)--10(-3) microng/ml) fragment I potentiates ACTH-induced steroidogenesis. Fragment I has no effect on the lipolysis;however, it potentiates ACTH-induced lipolysis at concentrations of 10--100 microng/ml. The results obtained support our previous supposition that "common" fragments are essential secondary non-specific active sites of hormones.