Specific binding of resiniferatoxin, an ultrapotent capsaicin analog, by dorsal root ganglion membranes.
We have previously demonstrated that resiniferatoxin (RTX), an unusual phorbol-related diterpene, induces similar responses in rodents to those induced by capsaicin, the pungent constituent of hot peppers (the genus Capsicum). Strikingly, RTX was 3-4 orders of magnitude more potent than was capsaicin. We report here specific binding of [3H]RTX to particulate preparations from dorsal root ganglia (DRG), a target tissue of both RTX and capsaicin action. The Kd was 0.27 nM for DRG from the rat; the Bmax was 160 fmol/mg. The respective values for pig DRG were 2.2 nM and 730 fmol/mg. Typical phorbol esters did not inhibit [3H]RTX binding. Capsaicin inhibited binding with 10(4)-fold lower affinity than RTX, consistent with the relative in vivo potencies. The specific [3H]RTX binding appears to represent the postulated capsaicin receptor.
Molecular Mechanisms of Tumor Promotion Section, National Cancer Institute, Bethesda, MD 20892.
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Szallasi
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Blumberg
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004224:Diterpenes / Q000378:metabolism*; D005260:Female; D005727:Ganglia, Spinal / Q000378:metabolism*; D007700:Kinetics; D010703:Phorbol Esters / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012044:Regression Analysis
D004224:Diterpenes; D010703:Phorbol Esters; C024353:resiniferatoxin; D002211:Capsaicin