alpha1A- but not alpha1B-adrenergic receptors precondition the ischemic heart by a staurosporine-sensitive, chelerythrine-insensitive mechanism.
OBJECTIVE
Brief periods of ischemia stimulate an endogenous mechanism in the heart that protects the myocardium from subsequent ischemic injury. alpha1-Adrenergic receptors (ARs) have been implicated in this process. However, the lack of sufficiently selective antagonists has made it difficult to determine which alpha1-AR subtype protects the heart from ischemic injury. The goal of this study was to identify the alpha1-AR subtype that is involved in ischemic preconditioning.


METHODS
We developed transgenic mice that express constitutively active mutant (CAM) forms of the alpha1A-AR or the alpha1B-AR regulated by their endogenous promoters. Hearts isolated from transgenic and non-transgenic mice were perfused by the Langendorff method using an ischemic preconditioning perfusion protocol or a non-preconditioning perfusion protocol prior to 30-min ischemia and 40-min reperfusion. Contractile function was continuously monitored through an intraventricular balloon.


RESULTS
The contractile function of non-transgenic hearts perfused according to the ischemic preconditioning protocol completely recovered from 30-min ischemia. However, non-transgenic hearts perfused according to the non-preconditioning protocol recovered only 60% of their contractile function. The contractile function of CAM alpha1A-AR hearts, but not CAM alpha1B-AR hearts, completely recovered from 30-min ischemia even though they were perfused according to the non-preconditioning protocol. Thus, CAM alpha1A-AR hearts, but not CAM alpha1B-AR hearts, were inherently preconditioned against ischemic injury. Staurosporine, but not chelerythrine, completely reversed the preconditioning effect of CAM alpha1A-ARs.


CONCLUSIONS
These data demonstrate that alpha1A-ARs protect the heart from ischemic injury through a staurosporine-sensitive signaling pathway that is independent of protein kinase C.
Rorabaugh
Boyd R
BR
Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, OH 44195, USA.
Ross
Sean A
SA
Gaivin
Robert J
RJ
Papay
Robert S
RS
McCune
Dan F
DF
Simpson
Paul C
PC
Perez
Dianne M
DM
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology*
C547714:Adra1a protein, mouse; C547717:Adra1b protein, mouse; D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D010617:Phenanthridines; D018340:Receptors, Adrenergic, alpha-1; C016299:chelerythrine; D011493:Protein Kinase C; D019311:Staurosporine