Concentration of substance P-like immunoreactivity (SPLI) in tissues of dog, rat and mouse.

The distribution of SPLI in various tissues from dog, rat and mouse was determined by radioimmunoassay. The gastrointestinal, urogenital and tracheobronchial tracts were found to contain SPLI with marked differences in levels in different parts of these tracts. Glandular tissues, such as salivary glands and pancreas, was well as eye, tongue and skin also contain SPLI. Species differences were encountered both in absolute amounts and the distribution of SPLI. The highest concentrations of SPLI were generally found in mouse followed by dog and rat. The present results are in agreement with those of previous studies in which SP was demonstrated by bioassay technique, but due to the greater sensitivity of the radioimmunoassay it was possible to show a much wider distribution of SP. Virtually all organs in which an effect of SP has been demonstrated also contain SPLI.