Angiology: Open Access
Open Access

Abstract

The Aortic Windkessel Property Adaptation in Whole-body Immersion Stressed Mice

Yang Wang, Annie Christel Bell, Han Wang, Boakye Kwabena, Shouyan Fan, Linghua Piao, Tong He, Zhibin Chen and Lingfeng Gao

Objective: Immersion induced hydrostatic pressure on thoracic cavity and limbs is one kind of cardiac overload model in simulating microgravity. We evaluated immersion hemodynamic parameters, investigated in vitro stretching induced aortic intact wall windkessel adaptations in whole-body immersion mice.
Method: Kunming mice were divided into immersion group (n=20) and control group (n=10) randomize. In immersion group, mice further divided into immersion group (n=10) and immersion with weight-bearing group (5% of body weight, n=10). The immersion kept 20 min/day in warm water and continues for 1 week. The hemodynamic parameters were collected by left carotid artery cannulation and analyzed by biological signal acquisition system. Calculi of percussion wave were calculated with integral mode to determine left ventricle stroke volume. In vitro aortic wall were prepared to a vascular ring and mechanical stretching the preparation to 1 g as the initial load. The preparations were further stretched by a micro-adjusting tuner with the interval of 5 min which gradually increasing 1 mm in each step. The stretching induced passive tension, where after, stress relaxation duration and myogenic spontaneous contraction were analyzed. In a separated preparation, myogenic contraction changes investigated in 0.05% Nitrendipine treated preparation.
Result: Mice carotid arterial pressure waveforms have significantly changed, however, mean arterial pressure were slightly increased but not significantly (immersion 9.14 ± 0.63 kPa, control 8.40 ± 0.97 kPa). The calculated stroke volume increased significantly (immersion 13.96 ± 0.12 μl/min, control 5.14 ± 0.69 μl/min, respectively). In vitro mechanical stretching induced less myogenic spontaneous contraction, stress relaxation period were shortening. Pre-treatment of 0.05% Nitrendipine induced more myogenic spontaneous contraction that revealed the spontaneous contraction was not solution Ca2+ influenced.
Conclusion: Immersion stress improved left ventricle functions that reflected in rapid ejection and isodiastolic period, suggested aortic windkessel properties were improved in microgravity simulation induced cardiac overload.