Proceedings of The Physiological Society

University of Edinburgh (2011) Proc Physiol Soc 25, PC29

Poster Communications

Reduction of vasomotion in thoracic aorta of immature rats using distilled water

J. Palacios1,4, J. Vega4, A. Paredes3, J. Bravo2, F. Cifuentes4

1. Dentistry, Universidad del Mar, Iquique, Chile. 2. Biomedicine, Antofagasta University, Antofagasta, Chile. 3. Chemistry, Antofagasta University, Antofagasta, Chile. 4. Experimental Physiology Laboratory, Antofagasta University, Antofagasta, Chile.

Rhythmical contraction known as vasomotion occurs in blood vessels. This phenomenon is observed under pathological conditions, and sometimes under physiological conditions. Vasomotion had been observed mainly in low resistance microcirculation vessels (Nilsson et al., 2003). Particular attention has been focused on cyclic variations of the aorta diameter in immature rats, in part because it may contribute to the regulation of blood flow (Haddock et al., 2005). The aim of the current study was to observe if immature rats have vasomotion in thoracic aorta and to determine the effect of tap water (control rats; 1-month-old) and distilled water (treated rats; 1-month-old) on vasomotion. In some experiments, immature Sprague-Dawley rats (1-month-old; 100 to 150 g) were compared with mature rats (4-month-old; 300 to 350 g). Animals were sacrificed by cervical dislocation. All groups drank tap water and distilled water from the time of weaning. In each experiment, we studied 6 to 8 adjacent aortic rings from the same animal, using a known method for isometric tension measurements (Palacios et al., 2006). The mechanical oscillations (vasomotion) observed in the aorta of the control group was influenced significantly by the concentration of phenylephrine (10-7 M PE; 136±4 mg maxima amplitude) and of KCl (20 mM; 110±4 mg maxima amplitude); this effect was diminished after 4 months (10-7 M PE; 31±8 mg maxima amplitude). The treated group did not show vasomotion in aorta (10-7 M PE; 5±2 mg maxima amplitude). Interestingly, the preincubation with EGTA of the control group eliminated the vasomotion phenomenon (10-7 M PE; 20±4 mg maxima amplitude). The aortic vasomotion and PE-induced tension were dependent on extracellular calcium concentration (0 to 1 mM Ca2+). It is possible that endothelial nitric oxide (NO) could be involved in vasomotion of immature rats; however, the oscillations were initiated only after the reduction in tension by acetylcholine (10-7 M) or NO (10-8 M). Therefore, the increase in vasomotion seems to be always associated with a reduction in tension to an intermediate level of the vasomotor tone. Vascular relaxation to ACh reduced in treated rats compared to control rats. We conclude that vasomotion in immature rats is associated with the calcium in drinking water, among other factors.

Where applicable, experiments conform with Society ethical requirements