Published Online
on July 23, 2007

A more recent version of this article appeared on October 1, 2007

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Submitted on May 21, 2007
Revised on June 6, 2007

Training-Induced Pressure Fall in Spontaneously Hypertensive Rats Is Associated With Reduced Angiotensinogen mRNA Expression Within the Nucleus Tractus Solitarii

Jorge Vinicius Cestari Felix and Lisete Compagno Michelini^*

From the Department of Physiology and Biophysics, Institute of Biomedical Sciences, Universidade de Sáo Paulo, Sáo Paulo, Brazil.

^* To whom correspondence should be addressed. E-mail: michelin{at}usp.br.

Abstract--Knowing that exercise training reduces arterial pressure in hypertensive individuals and that pressure fall is accompanied by blockade of brain renin-angiotensin system, we sought to investigate whether training (T) affects central renin-angiotensin system. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto controls (WKY) were submitted to training or kept sedentary (S) for 3 months. After functional recordings, brain was removed and processed for autoradiography (brain stem sequential slices hybridized with ³⁵S-oligodeoxynucleotide probes for angiotensinogen [Aogen] and angiotensin II type 1 [AT_1A] receptors). Resting arterial pressure and heart rate were higher in SHR_S (177±2 mm Hg, 357±12 bpm versus 121±1 mm Hg, 320±9 bpm in WKY_S; P<0.05). Training was equally effective to enhance treadmill performance and to cause resting bradycardia (-10%) in both groups. Training-induced blood pressure fall (-6.3%) was observed only in SHR_T. In SHR_S (versus WKY_S) AT_1A and Aogen mRNA expression were significantly increased within the NTS and area postrema (average of +67% and +41% for AT_1A and Aogen, respectively; P<0.05) but unchanged in the gracilis nucleus. Training did not change AT_1A expression but reduced NTS and area postrema Aogen mRNA densities specifically in SHR_T (P<0.05 versus SHR_S, with values within the range of WKY groups). In SHRs, NTS Aogen mRNA expression was correlated with resting pressure (y=5.95x +41; r=0.55; P<0.05), with no significant correlation in the WKY group. Concurrent training-induced reductions of both Aogen mRNA expression in brain stem cardiovascular-controlling areas and mean arterial pressure only in SHRs suggest that training is as efficient as the renin-angiotensin blockers to reduce brain renin-angiotensin system overactivity and to decrease arterial pressure.

Key words: angiotensin II • angiotensin receptors • blood pressure • heart rate • hypertension • experimental • rats

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