Lipolytic and Antilipolytic Effects of Human Growth Hormone,Its 20-Kilodalton Variant,A Reduced and Carboxymethylated Derivative,and Human Placental Lactogen on Chicken Adipose Tissue In Vitro

Abstract

The lipolytic and antilipolytic effects of human growth hormone (22K-hGH), its 20-kilodalton variant (20K-hGH), a reduced and S-carboxymethylated derivative (RCM-hGH), and human placental lactogen were examined using chicken adipose tissue explants in vitro. Lipolysis, as determined by glycerol release, was stimulated by 22K-hGH (biosynthetic and pituitary derived), 20K-hGH (pituitary derived), and RCM-hGH (modified biosynthetic). These growth hormone preparations also exhibited similar antilipolytic activity (i.e., transient inhibition of glucagon-induced lipolysis). However, unlike human growth hormone, human placental lactogen neither stimulated lipolysis nor inhibited glucagon-stimulated lipolysis. Some augmentation of glucagon-stimulated lipolysis was observed in the presence of human placental lactogen. These results indicate that the disulfide bridges (Cys⁵³ → Cys¹⁶⁵; Cys¹⁸² → Cys¹⁸⁹) and amino acid residues 32–46 of hGH are not required for lipolytic or antilipolytic activities of human growth hormone on chicken adipose tissue.