Abstract: Described are derivatives of the precursor peptide of the cardiodilatin/atrial sodiuretic factor (CDD-ANF) or fragments thereof which comprise at least the amino acid sequence of alpha-hANaP. The derivatives according to the present invention are compounds of the formula (I) ##STR1## X is a phosphate or thiophosphate group. R is NH.sub.2 or a peptide fragment from the amino acid sequence of gamma-hANaP. Radio-labelled derivatives are also possible. A method for the qualitative and/or quantitative determination of peptides containing the sequence of alpha-hANaP and a use of the compounds having the formula (I) as medicaments for various vaso- and renal related disorders are further described.

Abstract: Described is a peptide fragment which comprises the amino acid sequence 95-126 of ANF/CDD 1-126 (gamma-hANaP) and is formed in the kidney. The fragment urodilatin (ANF/CDD 95-126) has the following amino acid sequence: ##STR1## wherein R.sup.1 and R.sup.2 each represent further peptide fragments of ANF/CDD 1-126 (gamma-hANaP). In the amino acid sequence R.sup.1 is Thr-Alo-Pro-Arg-Ser-Leu-Arg-Arg-Ser-Ser and R.sup.2 is Asn-Ser-Phe-Arg-Tyr. Further described are processes for the preparation and/or recovery of the new peptide fragment and a medicament containing urodilatin (ANF/CDD 95-126 ) as well as medical indications of the medicament.