Abstract
In the last years, reactive oxygen species (ROS) have been proposed as mediators of proliferative/hypertrophic responses to angiotensin II (Ang II), both in vivo and in vitro. However, the hypothesis that the Ang II-dependent cell contraction could be mediated by ROS, particularly H2O2, has not been tested. Present experiments were devoted to test this hypothesis and to analyze the possible mechanisms involved. Catalase (CAT) prevented the increased myosin light chain phosphorylation and the decreased planar cell surface area (PCSA) induced by 1 μM Ang II in cultured rat vascular smooth muscle cells (VSMC). This preventive effect of CAT was also detected when 1 μM platelet-activating factor (PAF) was used as a contractile agonist instead of Ang II. Similar results were found when using horseradish peroxidase as an H2O2scavenger or cultured rat mesangial cells. In vascular smooth muscle cells, CAT modified neither the binding of labeled Ang II nor the Ang II-induced inositol 1,4,5-trisphosphate (IP3) synthesis. However, it completely abolished the Ang II-dependent calcium peak, in a dose-dependent fashion. CAT-loaded cells (increased intracellular CAT concentration over 3-fold) did not show either a decreased PCSA or an increased intracellular calcium concentration after Ang II treatment. Ang II stimulated the H2O2 synthesis by cultured cells, and the presence of CAT in the extracellular compartment significantly diminished the Ang II-dependent increased intracellular H2O2 concentration. The physiological importance of these findings was tested in rat thoracic aortic rings: CAT prevented the contraction elicited by Ang II. In summary, present experiments point to H2O2 as a critical intracellular metabolite in the regulation of cell contraction.
Footnotes
- Received May 8, 2000.
- Accepted August 16, 2000.
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Send reprint requests to: Diego Rodriguez Puyol, Department of Physiology, School of Medicine, Universidad de Alcalá, Carretera de Barcelona, Km. 33.600, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain. E-mail:diego.rodriguez{at}alcala.es
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The present experiments were supported by the Instituto de Salud Carlos III (FIS 95/0021–00) and the Comision Interministerial de Ciencia y Tecnologia (SAF 98/0054). G. Torrecillas is funded by the Ministerio de Educacion y Cultura and S. Lopez Ongil is funded by the Comunidad Autonoma de Madrid.
- The American Society for Pharmacology and Experimental Therapeutics
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