1. Hypertension Unit, Heart Institute-InCor, Medical School,
2. Laboratory of Cardiovascular Physiology, Department of Physiology, Basic, and Health Sciences Institute, University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 90050 – 170, Brazil
3. Conselho Nacional de Desenvolvimento Cientı́fico e Tecnológico Programa Institucional de Bolsas de Iniciaç̃o Científica,
4. Divisão de Bioengenharia, Heart Institute, Medical School, University of São Paulo, São Paulo, São Paulo 5403–000; and