1-RECEPTOR OR ADENOSINE A1-RECEPTOR DEPENDENT PATHWAY ALONE IS NOT SUFFICIENT BUT SUMMATION OF THESE PATHWAYS IS REQUIRED TO ACHIEVE AN ISCHAEMIC PRECONDITIONING EFFECT IN RABBITS
Authors: Baba, Kaori1; Minatoguchi, Shinya1; Zhang, Chengxi1; Kariya, Tatsuya1; Uno, Yoshihiro1; Kawai, Takao1; Takahashi, Masahiko1; Takemura, Genzou1; Fujiwara, Hisayoshi1
Source: Clinical and Experimental Pharmacology and Physiology, Volume 32, Number 4, April 2005 , pp. 263-268(6)
Publisher: Blackwell Publishing
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Abstract:
SUMMARY 1. It is reported that1-receptors and adenosine A1-receptors are involved in the ischaemic preconditioning (PC) effect on infarct size (IS). However, it is still unclear to what extent 1-receptors and adenosine A1-receptors contribute to the mechanism of PC. Therefore, we investigated the extent of the contribution of 1-receptors and adenosine A1 receptors to the PC effect on IS and examined the relationship between these receptors and protein kinase C. 2. Infarct size was measured in rabbits subjected to 30 min ischaemia and 48 h reperfusion. Tyramine (Tyr) was intravenously administered before 30 min ischaemia in the absence or presence of bunazosin (BN, 1-receptor blocker) and staurosporine (ST), a protein kinase C inhibitor, respectively. R(-)N6-(2-phenylisapropyl)-adenosine (PIA), a selective adenosine A1 agonist, was intravenously administered before 30 min ischaemia in the absence or presence of 8-p-sulphophenyltheophylline (8SPT), an adenosine blocker and ST, respectively. In the PC groups, BN, BN + PIA, 8SPT, 8SPT + Tyr or placebo saline was injected before or during PC. 3. Both Tyr and PIA reduced the IS, which was blocked by BN and 8SPT, respectively. The IS-reducing effect of Tyr or PIA was blocked by ST. The IS-reducing effect of PC was completely blocked by BN and 8SPT, respectively. The blocking effect of BN on the IS-reducing effect of PC was abolished by adding PIA during PC ischaemia. The blocking effect of 8SPT on the IS-reducing effect of PC was abolished by adding Tyr before PC ischaemia.4. These data suggest that an 1-receptor dependent pathway exists and an adenosine A1-receptor dependent pathway, stimulation of both of which activates protein kinase C, then reduces the IS. However, exclusive stimulation of a single 1-receptor dependent pathway or a single adenosine A1-receptor dependent pathway alone is not sufficient but the summation of these pathways is required to achieve a PC effect on IS in rabbits.
Keywords:
1-receptor;
adenosine A1-receptor;
infarct size;
ischaemic preconditioning;
protein kinase C
Document Type: Research article
DOI: 10.1111/j.0305-1870.2005.04185.x
Affiliations: 1: Second Department of Internal Medicine, Gifu University School of Medicine, Tsukasa-machi, Gifu, Japan
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