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- Title
A comparison of AT<sub>1</sub> angiotensin II antagonists at pre- and postjunctional angiotensin II receptors of the rat tail artery.
- Authors
Pinheiro, H.; Moura, D.; Albino-Teixeira, A.; Alves, C.; Torres, L.; Guimaráes, S.
- Abstract
A comparison was made of the influence of candesartan, ZD7155, losartan and eprosartan on angiotensin II effects at pre- and postjunctional AT1 receptors of the rat tail artery. To study the anti-angiotensin II effect at prejunctional receptors, the tissues were preincubated with [3H]noradrenaline and then superfused and electrically stimulated (1 Hz, 2 ms, 50 mA, during 5 min); to study the angiotensin II effect at postjunctional receptors, non-cumulative concentration-response curves to angiotensin II were determined in the absence and in the presence of the antagonist. pA2 values were calculated for competitive antagonists and pD'2 values for insurmountable antagonists. At the prejunctional level, losartan and eprosartan displayed competitive antagonism with pA2 values of 6.50 and 8.08, respectively, whereas candesartan and ZD7155 displayed non-competitive antagonism with pD'2 values of 8.71 and 7.98, respectively. At the postjunctional level, the four antagonists displayed the same kind of antagonism as prejunctionally with pA2 values for losartan and eprosartan of 8.52 and 8.22, respectively, and pD'2 values of 10.62 and 9.01, for candesartan and ZD7155, respectively. The ratios between post- and prejunctional potencies were: losartan 101, candesartan 81, ZD7155 11, and eprosartan 1.4. We conclude that, at least functionally, pre- and postjunctional angiotensin II AT1 receptors are different and propose that the prejunctional receptors in this tissue belong to the AT1B-subtype.
- Subjects
ANGIOTENSIN-receptor blockers; ANGIOTENSINS; NORADRENALINE; BIOTECHNOLOGY; CATECHOLAMINES; PHARMACOLOGY; NEUROTRANSMITTERS; DRUGS
- Publication
Naunyn-Schmiedeberg's Archives of Pharmacology, 2002, Vol 366, Issue 6, p537
- ISSN
0028-1298
- Publication type
Article
- DOI
10.1007/s00210-002-0645-8