Catecholamine-related gene expression correlates with blood pressures in SHR

In this study we aimed to determine whether the levels of gene expression for phenylethanolamine-N-methyltransferase (PNMT), noradrenaline transporter (NAT), α_1A-receptor (α_1A-R), and α_2Areceptor (α_2A-R) vary with resting systolic blood pressure in spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto (WKY) or Sprague-Dawley (SD) rats. Sites examined included central and peripheral regions associated with the control of arterial pressure. Twenty week old SD (n=6), WKY (n=6), and SHR (n=6) were used. Systolic blood pressure was measured using tail cuff plethysmography 2 weeks before tissue extraction. RNA was isolated and reverse-transcribed into cDNA. Gene expression levels were measured, using quantitative real time PCR, relative to the expression of GAPDH. PNMT, NAT, and α_1A-R mRNA expression was significantly greater in SHR tissue samples compared with normotensives. In the rostral ventrolateral medulla, PNMT mRNA in SHR was 3 times greater than that in WKY (SHR: 0.82±0.02%; WKY: 0.29±0.02%). The amount of α_2A-R mRNA was significantly lower in SHR compared with normotensives. For example, the level of α_2A-R mRNA in spinal cord of SHR was 3 times less than that found in WKY (SHR: 1.85±0.04%; WKY: 3.26±0.07%). PNMT, NAT, and α_1A-R mRNA levels were positively correlated with systolic blood pressure in all central tissue investigated. Conversely, α_2A-R mRNA levels in central sites were negatively correlated with systolic blood pressure. Clearly, a decrease in central α_2A-R and an increase in α_1A-R is consistent with the elevated blood pressure and sympathetic activity observed in SHR.