A Substance with Immunoreactivity to the Peptide Physalaemin in Mammalian Respiratory Tissue

Abstract

Physalaemin (Mr = 1284) is a potent undecapeptide from the skin of South American frogs. The amino acid sequence of the COOH-terminal region of this peptide is similar to that of substance P. An antiserum specific for the NH2-terminal sequence of physalaemin enabled the quantitation and localization of physalaemin-like immunoreactivity (PSLI) in mammalian tissues. PSLI is found in acid extracts of whole trachea from rat, rabbit, and guinea pig and in the tracheal mucosal layer in the dog, cow, and pig. The concentration determined by radioimmunoassay ranged from 1 to 15 ng/g dry weight of tissue, with rat trachea containing the highest amount. Gel filtration of an extract of rabbit trachea on Bio-Gel P-4 revealed a single peak of immunoreactivity that had an approximate Mr of 1700, similar to that detected in extracts of guinea pig and rabbit stomach. In contrast to amphibian physalaemin, mammalian PSLI 1) has a higher molecular weight, 2) is resistant to alpha-chymotrypsin or trypsin digestion, 3) elutes earlier from a C18 alkylsilane resin with increasing concentrations of methanol, and 4) can be separated from physalaemin by thin-layer chromatography. These data indicate that the mammalian PSLI is different in structure from the amphibian peptide.

The Significance of NK1 Receptor Ligands and Their Application in Targeted Radionuclide Tumour Therapy

“…Multiple groups have recently published research concerning SP and its analogues or derivatives as agonistic or antagonistic peptide NK1R ligands [7,8,19,21,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65]. New unnatural peptides are designed in order to improve their biological properties (e.g., half-life, receptor affinity and lipophilicity).…”

“…There are also non-mammalian NK1R ligands belonging to the tachykinin family. These compounds have distinctly different structure from SP, however in COOH-terminal region they have similar pentapeptide sequence Phe-(Tyr/Ile)-Gly-Leu-Met-NH 2 (often referred as the “message domain”) [8,19,62,63,64,65] (Table 1). The non-mammalian tachykinins display the same spectrum of activity as the mammalian tachykinins and bind to the same receptors.…”