The Somatomedins: A Family of Insulinlike Hormones under Growth Hormone Control

Publisher Summary This chapter explains that growth hormone itself exercises no direct metabolic action on skeletal tissue, but rather acts through a second substance, which is detectable both in normal plasma and in plasma from hypophysectomized rats after growth hormone administration. The term sulfation factor is applied to this plasma activity because the assay used for its detection depends upon the in vitro incorporation of radioactive sulfate into proteoglycans of cartilage. The chapter describes with evidence that several distinct growth hormone dependent substances are responsible for the biological activity of plasma in sulfation factor assays and that these substances are all insulin-like; thus, these substances are components of non-suppressible insulin-like activity (NSILA). These insulin-like growth-promoting peptides has much in common with the elusive serum growth factors that are required for the proliferation of cells in tissue culture. The chapter also discusses that the sulfation factor plays a much more pervasive role in somatic growth. The term somatomedin encompasses all growth hormone-dependent plasma factors that mediate the growth of responsive tissues..