A metabolically stable and non-immunogenic peptide analog completely hydrosoluble at physiological pH having a peptide covalently linked to a fluorocarbon group, directly or through a linker which is a peptide having from 1 to 6 amino acids, either on the alpha-amino or the epsilon-amino group of at least one lysine of said peptide, when the linker is a lysine, the fluorocarbon group is directly linked to the epsilon-amino group of said linker; said peptide analog being selected from: i) an apelin analog having said peptide of the formula: and wherein Xaa1 is L- or D-glutamine (QL or QD) or alanine; Xaa2 is arginine or lysine or D-norleucine (Nle); Xaa3 is serine or alanine; Xaa4 is histidine or alanine; Xaa5 is lysine or norleucine (Nle); Xaa6 is methionine, leucine, phenylalanine or norleucine (Nle); Xaa7 is phenylalanine, 4-Br phenylalanine (4-BrF), 4-(Obenzyl)phenylalanine (4-ObnF) or p-benzoyl phenylalanine (Bpa); and ii) an apelin analog with an amino acid sequence having at least 80% identity with the sequence of (i). or iii) an angiotensin II analog having said peptide of the formula: and wherein Xaa1 is aspartic acid or sarcosine; Xaa2 is phenylalanine or OH; and iv) an angiotensin II analog with an amino acid sequence having at least 80% identity with the sequence of (iii). or v) an oxytocin analog having said peptide of the formula: and wherein Xaa1 is glutamine or threonine; Xaa2 is proline or glycine; Xaa3 is leucine, lysine or proline; vi) an oxytocin analog with an amino acid sequence having at least 80% identity with the sequence of (v); but excluding an apelin analog having the following peptide of formula: wherein said peptide of formula is linked to a fluorocarbon group, an acetyl group, or an acyl group -C R where R is a C 7-30 alkyl, directly or through a linker selected from the group consisting of PEG, lysine and arginine, either on the alpha-amino or the epsilon-amino group of at least one lysine of the peptide formula, and when the linker is a lysine, the fluorocarbon group, acetyl or acyl group is directly linked either on the epsilon-amino group of said linker and wherein: Xaa1 is arginine or D-isomer arginine (R D); Xaa2 is glutamine or D-isomer glutamine (Q D) Xaa3 is leucine or D-isomer leucine (L D); Xaa4 is histidine or α-aminoisobutyric acid (Aib); Xaa5 is alanine or D-isomer alanine (A D) or glycine; Xaa6 is methionine or norleucine (Nle); Xaa7 is phenylalanine of 4-Br phenylalanine (4-BrF). i) an apelin analog having said peptide of the formula: and wherein Xaa1 is L- or D-glutamine (QL or QD) or alanine; Xaa2 is arginine or lysine or D-norleucine (Nle); Xaa3 is serine or alanine; Xaa4 is histidine or alanine; Xaa5 is lysine or norleucine (Nle); Xaa6 is methionine, leucine, phenylalanine or norleucine (Nle); Xaa7 is phenylalanine, 4-Br phenylalanine (4-BrF), 4-(Obenzyl)phenylalanine (4-ObnF) or p-benzoyl phenylalanine (Bpa); and Xaa1 is L- or D-glutamine (QL or QD) or alanine; Xaa2 is arginine or lysine or D-norleucine (Nle); Xaa3 is serine or alanine; Xaa4 is histidine or alanine; Xaa5 is lysine or norleucine (Nle); Xaa6 is methionine, leucine, phenylalanine or norleucine (Nle); Xaa7 is phenylalanine, 4-Br phenylalanine (4-BrF), 4-(Obenzyl)phenylalanine (4-ObnF) or p-benzoyl phenylalanine (Bpa); and ii) an apelin analog with an amino acid sequence having at least 80% identity with the sequence of (i). or iii) an angiotensin II analog having said peptide of the formula: and wherein Xaa1 is aspartic acid or sarcosine; Xaa2 is phenylalanine or OH; and Xaa1 is aspartic acid or sarcosine; Xaa2 is phenylalanine or OH; and iv) an angiotensin II analog with an amino acid sequence having at least 80% identity with the sequence of (iii). or v) an oxytocin analog having said peptide of the formula: and wherein Xaa1 is glutamine or threonine; Xaa2 is proline or glycine; Xaa3 is leucine, lysine or proline; Xaa1 is glutamine or threonine; Xaa2 is proline or glycine; Xaa3 is leucine, lysine or proline; vi) an oxytocin analog with an amino acid sequence having at least 80% identity with the sequence of (v); but excluding an apelin analog having the following peptide of formula: wherein said peptide of formula is linked to a fluorocarbon group, an acetyl group, or an acyl group -C R where R is a C 7-30 alkyl, directly or through a linker selected from the group consisting of PEG, lysine and arginine, either on the alpha-amino or the epsilon-amino group of at least one lysine of the peptide formula, and when the linker is a lysine, the fluorocarbon group, acetyl or acyl group is directly linked either on the epsilon-amino group of said linker and wherein: Xaa1 is arginine or D-isomer arginine (R D); Xaa2 is glutamine or D-isomer glutamine (Q D) Xaa3 is leucine or D-isomer leucine (L D); Xaa4 is histidine or α-aminoisobutyric acid (Aib); Xaa5 is alanine or D-isomer alanine (A D) or glycine; Xaa6 is methionine or norleucine (Nle); Xaa7 is phenylalanine of 4-Br phenylalanine (4-BrF). Xaa1 is arginine or D-isomer arginine (R D); Xaa2 is glutamine or D-isomer glutamine (Q D) Xaa3 is leucine or D-isomer leucine (L D); Xaa4 is histidine or α-aminoisobutyric acid (Aib); Xaa5 is alanine or D-isomer alanine (A D) or glycine; Xaa6 is methionine or norleucine (Nle); Xaa7 is phenylalanine of 4-Br phenylalanine (4-BrF).