Bombesin-like immunoreactivity in mammalian tissues

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Abstract
Antiserum directed to the amphibian bomesin was raised in a guinea pig using the conjugate of N.alpha.-glycyl-[1-Glutamine]-bombesin with bovine serum albumin. The major immunologic determinant of this antiserum GP-3303 was in the 6-7 sequence of bomesin. Bombesin-like immunoreactivities in gastrointestinal tissue extracts of the pig, dog, monkey, rat and guinea pig were extremely low when measured by the present radioimmunoassay system using antiserum GP-3303. The porcine gastrin releasing peptide recently isolated has the same decapeptide sequence as bombesin (5-14) in the C-terminal region except for the amino acid in position 7 of the bombesin molecule. The very low concentrations of bombesin-like immunoreactivity in the mammalian tissue extracts examined in the present study seem to reflect, at least in part, this amino acid substitution in the position corresponding to position 7 of bombesin, since the amino acid is involved in the major immunologic determinant of antiserum GP-3303. The bombesin-like immunoreactivity detected in mammalian tissues may be due to a new group of peptides in which the porcine gastrin releasing peptide is included.