Localization and Regulation of Phenylethanolamine N‐Methyltransferase Gene Expression in the Heart of Rats and Mice during Stress

Abstract

Recently we have described the existence of phenylethanolamine N-methyltransferase (PNMT) mRNA in the heart of adult rats. In this study, we report the first data on distribution of the PNMT protein in rat hearts, which follows the distribution of PNMT mRNA (high levels in the atria and low levels in ventricles). The main aim of this study was to determine the localization of the PNMT mRNA in the heart and to examine whether gene expression of this enzyme is affected by immobilization (IMO) stress in a time-dependent manner. PNMT mRNA levels were detected in all seven studied parts of the heart (atria without and with intramural ganglion cells, ventricles, and septum), with the highest levels in the left atrium and its ganglionic part. Both Southern blot and sequencing verified the specificity of PNMT detected by RT-PCR. Single IMO for 2-h increased gene expression of PNMT, as determined by both RT-PCR and Real-Time PCR in the right and left atria. Surprisingly, the ganglionic parts of the atria did not respond to stress stimulation. Peak levels of PNMT mRNA were found in the 3-h interval after the IMO terminated, and also 24 h after the first or sixth IMO. Expression of aromatic L-amino acids decarboxylase and dopamine-beta-hydroxylase has also been detected in the heart of control and stressed rats. In the atria, the effect of stress is clearly modulated by glucocorticoids, since in mice with corticotrophin-releasing hormone knocked out gene the immobilization-induced increase in the PNMT mRNA levels seen in wild-type animals was abolished. Thus, our data have shown that gene expression of the PNMT is localized, not predominantly in cardiac ganglion cells, but in a wide range in atrial cardiomyocytes. Mechanism responsible for the regulation of stress-induced increase of PNMT gene expression in cardiac atria is clearly dependent on the presence of glucocorticoids.

Effect of immobilization stress on gene expression of catecholamine biosynthetic enzymes in heart auricles of socially isolated rats

“…Immobilization stress is one of the most intensive stimuli. Single or repeated immobilization for 7 days has been shown to produce an increase of PNMT mRNA levels both in atria and ventricles (32,33). Interestingly, the additional immobilization applied in the present study did not affect the gene expression of catecholamine biosynthetic enzymes and enzymatic proteins in the right and left auricles of chronically stressed animals, suggesting that the response to stress depends on prior experience with stressors.…”

Adrenaline and Noradrenaline: Partners and Actors in the Same Play"

“…Furthermore, glucocorticoids levels are very important in the expression of PMNT and thus in the rate of ADR synthesis. Glucocorticoids are very relevant in the size of the stores of ADR available for release in the brain (Moore and Phillipson, 1975b, a), adrenal medulla (Kelner and Pollard, 1985, Stachowiak et al, 1988, Wan and Livett, 1989, Ross et al, 1990, Betito et al, 1992, Wong et al, 1992, heart (Kennedy and Ziegler, 1991, Krizanova et al, 2001, Kvetnansky et al, 2004 or lungs (Kennedy et al, 1993). The activities of both tyrosine hydroxylase and dopaminehydroxylase are also increased in the adrenal medulla under the influence of glucocorticoids (Carroll et al, 1991).…”

Expression Levels of mRNAs for Catecholamine Biosynthetic Enzymes as Markers of Acute Response to Contusion Stress during the Early Postmortem Period

“…Moreover, most of the methods in the analysis including Southern blotting and semi-quantitative reverse trancrptional polymerase chain reaction (RT-PCR) (Nankova et al 1994;Nankova et al 1996;Brooks et al 1997;Lai et al 2000;Kubovcakova et al 2004;Gallara et al 2004;Lai et al 2005), require some experience to produce reliably reproducible results. In recent years, real-time quantitative PCR (RQ-PCR) has been established as a simplified and reproducible method for the quantification of mRNA expression, and some investigators have used this technique for assaying levels of catecholamine mRNA expression (Bornstein et al 1999;Kvetnansky et al 2004;Herradón et al 2006). However, these authors only compared catecholamine levels between stress and nonstress conditions, and not between different stress conditions.…”