PEPTIDE USEFUL AS SOMATOSTATIN ANTAGONIST

PROBLEM TO BE SOLVED: To obtain the subject new peptide, comprising a peptide having a specific amino acid sequence, having somatostatin antgonist activities, capable of increasing the production, etc., of a growth hormone, insulin and a gastric enzyme, etc., and useful for promoting immunological functions and growth, etc. SOLUTION: This new peptide (salt) has formula I [AA2 is the D- or L-isomer of Phe, Tyr, Trp or His; AA3 is the D-isomer of a (substituted)alkylamino acid; AA4 is the D- or L-isomer of Arg, Lys, His, Asp, Gln, Tyr, Ile, Pro or Trp; AA5 is the D- or L-isomer of Trp, Ile, Phe, Tyr or Cys; AA6 is the D- or L-isomer of Phe, Try, Ala, Leu, Ile, Met, Gln, Trp, Asn or Thr; (m), (n) and (p) are each 0 or 1], formula II or III and pure somatostatin antagonist activities and is capable of increasing the release of a growth hormone, insulin, a glucagon and a gastric enzyme in mammals and promoting the growth and immunological functions.