Gellerfors, P., Pavlu, B., Axelsson, K., NyhlCn, C., Johansson, S. (Kabi Peptide Hormones, Stockholm, Sweden). Separation and identification of growth hormone variants with high performance liquid chromatography techniques. Acta Paediatr &and [SUPPI] 370: 93-100, 1990. Liquid chromatography techniques were used to separate and identify human growth hormone (hGH) variants. N-terminal modified forms, such as des-Phe (2-191) and methionyl-hGH (met-l-191), were separated from recombinant human growth hormone (rhCH (1-191)) by hydrophobic interaction chromatography (HIC). A proteolytically cleaved ('clip') form of rhCH which has a break in the polypeptide chain between Thr (142) and Tyr (143), also proved to be separable from rhCH by HIC. In addition, a mutated form of rhCH with only two amino acid substitutions, Glu(65) to Val(65) and Glu(66) to Lys (66), on a random coil domain of the molecule, was separated from rhCH by HIC, indicating that these substitutions altered the hydrophobicity of the molecule. Treatment of rhCH with hydrogen peroxide led to sulphoxide formation in two methionine residues Met(l4) and Met (125); it was not possible to oxidize Met(l70). The oxidized forms of rhGH were readily separated from rhGH(1-191) by reversed-phase chromatography. Analyses of rhCH batches showed very low levels (< 0.3%) of oxidized rhCH, indicating that rhCH is highly resistant to oxidative reactions. Deamidations were induced in rhCH by heat treatment. The primary deamidation site was found to be Asn(149). Monodesamido rhGH and didesamido rhGH were efficiently separated from rhCH(1-191) by anion-exchange chromatography. Key words: High performance liquid chromatography, growth hormone variants, hydrophobic interaction chromatography, recombinant human growth hormone;'Genotropin, trademark KabiVitrum AB. Sweden. for recombinant somatropin; Genotonom in Belgium, France and Spain.