PT  - JOURNAL ARTICLE
AU  - A Szallasi
AU  - N E Lewin
AU  - P M Blumberg
TI  - Identification of alpha-1-acid glycoprotein (orosomucoid) as a major vanilloid binding protein in serum.
DP  - 1992 Sep 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 883--888
VI  - 262
IP  - 3
4099  - http://jpet.aspetjournals.org/content/262/3/883.short
4100  - http://jpet.aspetjournals.org/content/262/3/883.full
SO  - J Pharmacol Exp Ther1992 Sep 01; 262
AB  - We have used the vanilloid (capsaicin) receptor assay to search for modulators of binding activity. We report here that both capsaicin and its ultrapotent analog, resiniferatoxin (RTX), bind to the plasma protein alpha-1-acid glycoprotein (AGP) with high affinity (10.5 and 0.3 microM, respectively). AGP seems to be the dominant vanilloid (capsaicin/RTX) binding protein in serum. [3H] RTX binding to AGP is inhibited by chlorpromazine and by Trisbutoxyethylphosphate, indicating that vanilloids compete for a well-characterized drug binding domain on the AGP molecule. The 35-fold difference in the affinity of AGP for RTX and capsaicin may result in differences in the pharmacodynamics and pharmacokinetics of these two compounds; the contribution of AGP binding to the unique spectra of action of RTX or to the marked species differences in vanilloid actions, however, remains to be determined. An important practical application of AGP is its inclusion in the [3H]RTX binding assay utilizing sensory ganglion membranes to reduce nonspecific binding by up to 5-fold.