Distribution of alpha1-adrenergic receptor mRNA species in rat heart.
Radioligand binding studies have detected alpha1A- and alpha1B-adrenergic receptors (AR) in rat heart, but the ligands available for these studies lack the sensitivity and specificity needed to map possible differences in alpha1-AR subtype expression. We therefore used competitive reverse transcriptase-polymerase chain reaction (RT-PCR) techniques to measure steady-state amounts of alpha1-AR messenger RNA (mRNA) subtypes in tissue dissected from several regions of rat heart. We detected mRNA for alpha1A-, alpha1B-, and alpha1D-AR in each region. Irrespective of the alphaAR subtype, the total number of alpha1-AR transcripts has the following regional rank order: left ventricular papillary muscle > left ventricle > left atrium > apex > right ventricle > ventricular septum > right atria. Among the regions, the fractional contribution of alpha1A-, alpha1B-, and alpha1D-AR mRNA to the total amount of alpha1-AR displays considerable variability. The alpha1B-AR mRNA accounts for >50% of the total alpha1-AR mRNA in all regions except the ventricular septum. There are also significant percentages of alpha1A-AR in each region, especially in the papillary muscle (48%) and ventricular septum (48%). The alpha1D-AR mRNA transcripts are found in comparatively low numbers; their highest levels (18% of total) were found in the right ventricle. These differences in alpha1-AR mRNA expression may contribute to the observed regional differences in myocardial responses to alpha1-AR agonists and antagonists.
Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska 68178, USA.
D W
DW
Wolff
H K
HK
Dang
M F
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Liu
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Jeffries
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Scofield
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000096:biosynthesis*
D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1