Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA190

Poster Communications

Mechanosensitive mechanisms responsible for the exercise-induced increased autoregulatory range of coronary arterioles.

A. Koller1,2,3, G. Nadasy5, F. Ihász6, G. Dornyei4, M. Szekeres4

1. Natural Sciences, University of Physical Education, Budapest, Hungary. 2. Faculty of Heath Sciences, Semmelweis University, Budapest, Hungary. 3. Physiology, New York Medical College, Valhalla, New York, United States. 4. Morphology and Physiology, Semmelwies University, FHS, Budapest, Hungary. 5. Physiology, Semmelwies University, Budapest, Hungary. 6. Sportsciences, Eötvös Loránd University, Szombathely, Hungary.

Exercise elicits early adaptations of coronary vessels enabling the coronary circulation to provide greater blood flow during higher demands. Systolic blood pressure and diastolic blood flow greatly increase during exercise. Thus we hypothesized that short-term daily exercise induces biomechanical and functional remodeling of the coronary resistance arteries related to mechanosensitivity: pressure and flow/shear stress. Male rats were subjected to progressively increasing four-week treadmill exercise program (over 60min/day, one mph in the final step EX) whereas the other group remained sedentary (SED). Coronary arterioles (~120 μm in diameter at 50 mmHg) were isolated and their diameters were measured by television-microscopy. The biomechanical characteristics, the magnitude of myogenic and flow/shear stress responses and the contribution of endogenous nitric oxide and prostanoid production to diameter were assessed, by specific inhibitors. Arterioles isolated from exercised animals - compared to their sedentary mates - had thicker walls (~10 μm), increased distensibility (0.5 vs. 0.8 kPa-1), decreased elastic modulus (in low-pressure range) as a result of reduced wall stress (by ~15%). Arterioles of exercised rats exhibited a significantly greater myogenic constriction (SED: 102.1 vs. EX 80.1 μm) and flow/shear stress-induced dilation (diameter increase: 52.4±7.8 vs. 30.3±3.9 μm). Inhibition of nitric oxide synthase and cyclooxygenases reduced the diameter at the lower pressure range and eliminated flow/shear stress-induced dilation. Indomethacin increased the diameter of arterioles at higher pressure range. In conclusion, short-term daily exercise induces morphological and functional remodeling of rat intramural coronary arterioles involving smooth muscle and endothelial mechanosensitive mechanisms, resulting in a greater constrictor and dilator reserves extending the range of coronary autoregulation contributing thereby to the optimization of coronary blood flow during exercise.

Where applicable, experiments conform with Society ethical requirements