Use of Gene Transfer to Increase Animal Growth

In mammals, somatic growth is controlled by a cascade of circulating hormones emanating from the hypothalamus, pituitary gland, and liver. Growth hormone (GH), an intermediate in this cascade, is a 22,000-dalton, single-chain polypeptide produced in acidophiles of the anterior pituitary gland. The regulation of GH secretion is mediated, in part, by two hypothalamic hormones that reach the pituitary via the hypothalamo-hypophyseal portal blood system. Somatostatin, a neuropeptide of 14 or 28 amino acids inhibits the release of GH while growth hormone-releasing factor (GRF) stimulates both GH synthesis and secretion. GH stimulates the production of somatomedin C or insulin-like growth factor I (IGF-I) which is thought to mediate postnatal somatic growth by binding to membrane receptors of peripheral mescenchymal cells.