Conformational Energy Studies and<i>in Vitro</i>and<i>in Vivo</i>Activity Data on Growth Hormone-Releasing Peptides*

A series of growth hormone-releasing peptides have been designed and tested for both in vitro and in vivo activity. In vitro activity at 1-10 ng/ml was obtained for the pentapeptide, His-DTrp-Ala-Trp-DPhe-NH2 (I) and the hexapeptide, His-DTrp-Ala-Trp-DPhe-Lys-NH2 (II). These peptides, as well as others to be described, are active in releasing GH in vivo at low microgram dosages. In this manuscript, the conformational properties and in vitro and in vivo activity of a series of small peptides are reported. Results of the biological studies are reported in an accompanying paper.