Metallothionein-human gh fusion genes stimulate growth of mice

The high level of expression of MThGH genes in some animals allows quantitation of messenger RNA (mRNA) concentrations in various tissues of transgenic animals. Transgenic mice expressing herpesvirus thymidine kinase have been unsatisfactory for these studies because the concentration of thymidine kinase mRNA is too low to quantitate in most tissues. Long-term stimulation by human growth hormone (hGH) delivered in the manner may be more effective than delivery based on injection or continuous infusion into newborn or adult animals. Growth is thought to result from activation of hepatic growth hormone receptors which in turn stimulate the synthesis and secretion of like growth factor-I, a 70-amino acid peptide hormone that circulates to peripheral tissues to stimulate their growth. The hGH concentrations of individual animals were relatively constant but varied from animal to animal.