Radioimmunoassay of substance P and its stability in tissue.

A sensitive and specific radioimmunoassay for substance P has been developed and its full characterisation is described. The assay was used to investigate the stability of substance P in tissue in order to establish the optimal conditions of tissue storage for maximal recovery of the peptide. The results indicate unexpected post-mortem changes in tissue substance P content and suggests its existence in at least two separate pools, which differ in their susceptibility to degradation. These results highlight the need for careful consideration of both extraction technique and assay characteristics in radioimmunological investigations of substance P.