ABSTRACT
Since the discovery of the first potent hexapeptide growth hormone-releasing peptide (GHRP-6) about 12 years ago (1), a range of compounds have been developed with varying potencies, including GHRP-1 and GHRP-2. The chemical structure and relative potency, in terms of GH, for these three peptides are summarized in Table 1. Most recently, Howard et a!. (2) identified a novel receptor in rat and swine pituitary glands that binds GHRP and nonpeptidergic GH secretagogues (GHS) with varying levels of affinity. Our work indicates that GHRP-2 acts on a receptor that is different from that employed by GHRP-6 or GHS (3,4). Thus, various subtypes of the GHRP-GHS receptor may exist, in ovine somatotrophs at least, and this chapter reviews our experimental evidence for this.
