Neuroendocrine Peptides - Analysis by Reversed Phase High Performance Liquid Chromatography

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Abstract
A high performance liquid chromatographic (HPLC) method is described for determining the biologically active neuroendocrine peptides thyrotropin releasing hormone (TRH), leucine (leu) and methionine (met) enkephalin, angiotensin II, delta sleep inducing peptide (DSIP), luteinizing hormone releasing hormone (LHRH), substance P and growth hormone release inhibiting factor (somatostatin). The selection of mobile phases was limited to these systems that do not exhibit strong absorbtion at 215 nm and 254 nm. Under isocratic conditions at room temperatures with the appropriate selection of mobile phase it was possible by reversed phase chromatography to resolve all of the peptides investigated. We can resolve with the systems employed peptides differing by only one amino acid in chain length as well as peptides differing by only one amino acid in the chain sequence. The method is rapid, does not require derivitization, can be used with aqueous matrixes and is sensitive in the nanomolar range. Our research has shown that most synthetic peptides lack purity and that all of the peptides except LHRH lack stability when stored in aqueous sterile solution at 8°C for four weeks. The implications of this latter finding are under investigation.