Activation of alpha 1-adrenoceptors is not essential for the mediation of ischaemic preconditioning in rat heart
Abstract
1. The aim of the present study was to clarify the role of alpha1-adrenoceptors in the mechanism of ischaemic preconditioning (IP). 2. Rat isolated perfused hearts were either non- preconditioned, preconditioned with 5 min ischaemia or treated for 5 min with alpha1-adrenoceptor agonists (50 micromol/L phenylephrine; 0.1, 0.5 and 1 micromol/L methoxamine) before being subjected to 45 min of sustained ischaemia followed by 60 min reperfusion. 3. Within each of the above protocols, hearts were divided into groups to which alpha1-adrenoceptor antagonists (prazosin, 5'-methyl urapidil and chloroethylclonidine (CEC)) were administered. Functional recovery and infarct size were used as indices of the effects of ischaemia. Ischaemic contracture characteristics and maximal diastolic pressure during reflow were also assessed. 4. Blockade of alpha(1)-adrenoceptors with prazosin or the subtype-selective antagonists 5'-methyl urapidil and CEC did not abolish the protective effect of IP with respect to both functional recovery and infarct size reduction. 5. Protection afforded by phenylephrine was attenuated in hearts treated with prazosin or the alpha(1B)-adrenoceptor- selective antagonist CEC, but not in those treated with the alpha(1A)-ad...Continue Reading
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