Premium
PACPX ‐ a substituted xanthine ‐ antagonizes both the A 1 and A 2 subclasses of the P 1 ‐purinoceptor: antagonism of the A 2 subclass is competitive but antagonism of the A 1 subclass is not
Author(s) -
Burnstock Geoffrey,
Hoyle Charles H.V.
Publication year - 1985
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1985.tb08859.x
Subject(s) - antagonism , xanthine , chemistry , stereochemistry , biochemistry , receptor , enzyme
1 1,3‐Dipropyl‐8‐(2‐amino‐4‐chlorophenyl)xanthine (PACPX) was examined for its ability to antagonize adenosine acting on the A 1 and A 2 subclasses of the P 1 ‐purinoceptor. A 1 ‐purinoceptors were studied in the isolated, driven left atria of the guinea‐pig, and A 2 ‐purinoceptors in the isolated, carbachol‐contracted taenia coli of the guinea‐pig. 2 PACPX antagonized the actions of adenosine in both types of preparation and was a more potent antagonist than 8‐phenyltheophylline. 3 The antagonism at the A 2 ‐purinoceptor was competitive with a pA 2 of 5.95. 4 The antagonism at the A 1 ‐purinoceptor was not competitive, although antagonism at the A 1 ‐purinoceptor was greater than that at the A 2 ‐purinoceptor, based on a comparison of pD 2 values. 5 The manner of antagonism of PACPX on the A 1 ‐purinoceptors of the heart was different from that found for the A 1 ‐receptors in bovine brain, implying that there is a fundamental difference between these central and peripheral A 1 subclasses of P 1 ‐purinoceptor.