Rapid degradation of [3H]-substance p in guinea-pig ileum and rat vas deferens in vitro.
The degradation of [3H]-substance P was monitored in guinea-pig ileum and rat vas deferens. Substantial and rapid metabolism occurred in both tissues within the time course of the pharmacological responses; for example, after 1 min more than 50% of the extracted tritium from both tissues was present in the form of metabolites. [3H]-inulin was used to estimate the rate of equilibration of the extracellular space of guinea-pig ileum longitudinal muscle and rat vas deferens with the bath fluid; half-lives of 30 s and 5 min respectively were observed. These two factors combine to give different concentrations of substance P in the biophase of the tissues. The peak concentration of substance P reached in the guinea-pig ileum longitudinal muscle was approximately five times higher than in the rat vas deferens. An analogue of substance P, [3H]-DiMe-C7, was found to be stable in both tissues. These results are discussed in the light of the suggested existence of multiple receptors for substance P, based on agonist potency differences.
D000818:Animals; D005110:Extracellular Space / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D066298:In Vitro Techniques; D007444:Inulin / Q000378:metabolism; D008297:Male; D051381:Rats; D013373:Substance P / Q000378:metabolism*; D014316:Tritium; D014649:Vas Deferens / Q000378:metabolism
D014316:Tritium; D013373:Substance P; D007444:Inulin