Concentration of substance P‐like immunoreactivity (SPLI) in tissues of dog, rat and mouse1

Abstract
The distribution of SPLI in various tissues from dog, rat and mouse was determined by radioimmunoassay. The gastrointestinal, urogenital and tracheobronchial tracts contained SPLI with marked differences in levels in different parts of these tracts. Glandular tissues such as salivary glands and pancreas, as well as eye, tongue and skin 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. Results agree with those of previous studies in which SP was demonstrated by bioassay technique, but the greater sensitivity of the radioimmunoassay showed a much wider distribution of SP. Virtually all organs in which an effect of SP has been demonstrated also contain SPLI.