TY - JOUR T1 - Specific binding of a 125I-labeled substance P analog to rat submaxillary gland. JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 116 LP - 123 VL - 230 IS - 1 AU - S W Bahouth AU - J M Stewart AU - J M Musacchio Y1 - 1984/07/01 UR - http://jpet.aspetjournals.org/content/230/1/116.abstract N2 - The substance P (SP) analog [tyrosine1, norleucine11]-substance P [( Tyr1, Nle11]-SP) was iodinated by the chloramine-T method to yield the mono iodinated derivative; both peptides were biologically active on the guinea-pig ileum SP receptor. Saturable, reversible binding of [125l-Tyr1, Nle11]-SP to a single class of noninteracting sites on the rat submaxillary gland homogenate was demonstrated with an affinity of 9.26 +/- 0.8 nM and a maximum binding of 15.7 +/- 1.25 or 250 +/- 20 fmol/mg of protein. The relative potencies of SP and its fragments SP(2-11) and SP(4-11), as measured by their IC50, are in agreement with their rank order in the salivation assay, whereas physalaemin was found apparently weaker than expected. However, their rank order in displacing [125I-Tyr1, Nle11]-SP was identical to their rank order in displacing [125I-Bolton-Hunter]-SP bound to mouse mesencephalic cells in primary culture. ER -