Ping P, Hammond H K
Veterans Affairs Medical Center, San Diego 92161.
Am J Physiol. 1994 Nov;267(5 Pt 2):H2079-85. doi: 10.1152/ajpheart.1994.267.5.H2079.
Right atrial and left ventricular homogenates have similar protein composition and beta-adrenergic receptor (beta-AR) numbers, but the right atrium has > 58% less adenylyl cyclase activity than the left ventricle. Associated with distinctive patterns of adenylyl cyclase activities are differences in G protein regulation between the two chambers. Compared with the left ventricle, the right atrium has 74% less Gs alpha mRNA (P < 0.0001) and 83% less G alpha i-2 mRNA (P < 0.002). When hearts are rapidly paced to produce heart failure, the left ventricle shows significant reductions in mRNA expression for both Gs alpha and G alpha i-2. However, the right atrium shows increased Gs alpha and G alpha i-2 mRNA expression. Despite divergent mRNA expression, Gs alpha and G alpha i-2 protein expression is down-regulated in both chambers in heart failure. In contrast, both chambers have similar beta 1- and beta 2-adrenergic receptor mRNA contents, and there is a selective reduction of beta 1-adrenergic receptor protein and mRNA in response to heart failure. Thus G protein and beta-AR mRNA regulation is regionally diverse in the heart. Physiological and anatomic differences between the right atrium and the left ventricle may dictate distinct patterns of adrenergic signaling and adaptations to stress.
右心房和左心室匀浆具有相似的蛋白质组成和β-肾上腺素能受体（β-AR）数量，但右心房的腺苷酸环化酶活性比左心室低58%以上。与腺苷酸环化酶活性的独特模式相关的是两个腔室之间G蛋白调节的差异。与左心室相比，右心房的Gsα mRNA减少74%（P < 0.0001），Gαi-2 mRNA减少83%（P < 0.002）。当心脏快速起搏导致心力衰竭时，左心室的Gsα和Gαi-2 mRNA表达显著降低。然而，右心房的Gsα和Gαi-2 mRNA表达增加。尽管mRNA表达存在差异，但心力衰竭时两个腔室的Gsα和Gαi-2蛋白表达均下调。相比之下，两个腔室的β1-和β2-肾上腺素能受体mRNA含量相似，并且心力衰竭时β1-肾上腺素能受体蛋白和mRNA有选择性减少。因此，心脏中G蛋白和β-AR mRNA调节在区域上是多样的。右心房和左心室之间的生理和解剖差异可能决定了肾上腺素能信号传导和应激适应的不同模式。
