DETERMINATION OF SUBSTANCE-P IN HUMAN NASAL LAVAGE FLUID

The determination of substance P (SP) concentrations in human nasal la vages can be used to monitor physiological and certain pathophysiologi cal processes in human airway mucosa. But, because of the low concentr ations, immunoassays of high sensitivity are needed. Two approaches to improve the sensitivity of the radioimmunological determinations of S P are compared: increasing the sample volume and miniaturizing the ass ay design. The characterization of SP-like immunoreactivity (SP-LIR) i n human nasal lavage was performed by investigating the immunological specificity of the antibody used in the radioimmunoassays and by rever sed-phase high-performance liquid chromatography separation of the SP- LIR. SP concentrations in nasal ravages can be reliably measured by ea ch of the two introduced RIA methods. Despite the lower detection limi t of the miniaturized immunoassay (0.2 in comparison to 1.3 fmol/incub ate) it is advisable to increase the sample volume in order to improve the sensitivity because of the higher precision of the determinations . SP-LIR was found in nasal lavage specimens in concentrations between 2 and 10 fmol/ml and consisted of authentic SP and, to a less extent, SP-sulfoxide.