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(Hypertension. 2007;50:780.)
© 2007 American Heart Association, Inc.

XVIIth Scientific Meeting of the Inter-American Society of Hypertension

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

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

Correspondence to Lisete Compagno Michelini, Department of Physiology and Biophysics, ICB, University of Sáo Paulo, Av Prof Lineu Prestes, 1524, 05508-900 Sáo Paulo, SP, Brazil. E-mail michelin{at}usp.br

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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