Substance P radioimmunoassay using Nalpha-tyrosyl-substance P and demonstration of the presence of substance P-like immunoreactivities in human blood and porcine tissue extracts.
Sensitive and specific radioimmunoassay for substance P was developed using synthetic substance P and 125I-Nalpha-tyrosyl-substance P. Substance P-human alpha-globulin conjugate was used for production of anti-substance P antisera in rabbits. Synthetic substance P was used as a standard and the dextran-coated charcoal method was employed to separate the free peptide from that bound to antibodies. No cross-reactions by physalaemin and eledoisin observed in this system proved its high specificity to substance P. Nalpha-Tyrosyl-substance P and [Tyr1]-substance P showed the displacement curves indistinguishable from that of the standard substance P. Neither substance P5-11 nor substance P6-11 competed with the tracer at the concentration used. The minimum measurable dose of substance P by the assay system was 2.5-5 pg/incubate. Utilizing the system, human plasma samples from 42 healthy volunteers of both sexes were shown to contain immunoreactive substance P in amounts that averaged 298 pg/ml in male and 251 pg/ml in female. Substance P-like immunoreactivity was also demonstrated in hot-water extracts of porcine duodenum, jejunum, ileum, cecum, middle colon, rectum, pancreas, stomach and pituitary. The highest concentration (379 ng/g wet weight of organ) was found in the pituitary, and the ileum (7.9 ng/g wet weight of organ) and jejunum (1.9 ng/g wet weight of organ) were rich in the contents.
D000818:Animals; D003429:Cross Reactions; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007082:Ileum / Q000032:analysis; D007106:Immune Sera; D007583:Jejunum / Q000032:analysis; D008297:Male; D010902:Pituitary Gland / Q000032:analysis; D011863:Radioimmunoassay / Q000379:methods*; D013373:Substance P / Q000031:analogs & derivatives / Q000032:analysis* / Q000276:immunology; D013552:Swine
D007106:Immune Sera; D013373:Substance P