Exercise training in swine promotes growth of arteriolar bed and capillary angiogenesis in heart

Abstract

Exercise training induces coronary vascular adaptations. The goal of this study was to contrast the effects of training on capillary and arteriolar growth. Minipigs were trained for 1, 3, 8, and 16 wk and compared with controls. Maximal O2 consumption increased continuously throughout the study. Capillary and arteriolar densities and diameters, and proliferation of vascular cells in these vessels, were determined in perfusion-fixed tissue. The arterioles were subdivided into five groups according to diameter: 10-19.9, 20-30, 31-40, 41-70, and 71-120 microgram. The total vascular bed cross-sectional area increased by 37% at 16 wk, mainly because of an increase in the number of the small arterioles and an increase in the diameter of the larger vessels. Capillary density increased at 3 wk and then returned to control levels by 16 wk; concomitantly, the number of arterioles (20-30 microgram) increased at 16 wk. We speculate that the "extra" capillaries observed at 3 wk were the source of the new arterioles.

Partial persistence of exercise-induced myocardial angiogenesis following 4-week detraining in the rat

“…The neoformation of myocardial blood capillaries in swimming-exercised animals was initially reported by Ljungqvist and Unge (1973) and related to the resulting cardiac hypertrophy observed. Since then, conXicting reports have been published (Laughlin and Tomanek 1987;Hudlicka et al 1992;White et al 1998;Efthimiadou et al 2006). As discussed by Brown (2003), such discrepancies may be due to the age of animals and to the timing of observations; for instance, it appears that exercise induces cardiac capillary growth, but this is rapidly followed by vascular remodeling, which leads to an increase in the number and size of arterioles (White et al 1998).…”

“…Since then, conXicting reports have been published (Laughlin and Tomanek 1987;Hudlicka et al 1992;White et al 1998;Efthimiadou et al 2006). As discussed by Brown (2003), such discrepancies may be due to the age of animals and to the timing of observations; for instance, it appears that exercise induces cardiac capillary growth, but this is rapidly followed by vascular remodeling, which leads to an increase in the number and size of arterioles (White et al 1998). Thus, reports on exercise-induced angiogenesis, which focus on capillary density fail to convey the global picture of exercise-induced increase in cardiac blood supply.…”

“…Exercise training oVsets many age-related gene expression changes (Bronikowski et al 2003;Iemitsu et al 2006), upregulates a number of cardioprotective and anti-oxidant proteins (Powers et al 2004, Marini et al 2007, improves contractile function and optimizes energy usage (Ventura-Clapier et al 2007). Moreover, exercise increases the need for oxygen supply in the cardiac muscle, which may be met by the induction of neo-angiogenetic and vascular remodeling processes (White et al 1998;Brown 2003); these, in turn, may trigger prevention of the adverse eVects of coronary artery stenosis and occlusion (Schaper and Ito 1996).…”

“…Despite general agreement about exercise-induced angiogenesis in skeletal muscle, myocardial angiogenesis is less established, especially after moderate exercise in post-pubertal animals (Hudlicka et al 1992;Brown 2003). White et al (1998) demonstrated in a swine heart model that capillary growth is limited only to the early phase of exercise training, and then gives rise to an increase in density and size of arterioles. By contrast, Efthimiadou et al (2006) reported a signiWcant increase in myocardial angiogenesis at the end of a 2-week intensive training protocol.…”

Physical Activity in the Prevention and Treatment of Coronary Artery Disease

“…In the trained heart, the consequence is unaltered capillary density, but there is a larger and more profound arterial supply 2, 47. However, the growth of vessels by angiogenesis is not restricted to capillaries; it is also evident at the level of arterioles (diameter, <30 μm), coronary resistance vessels (diameter, <300 μm), and large proximal conduit vessels 1, 2, 48…”