Geometric, Elastic and Contractile-Relaxation Changes in Coronary Arterioles Induced by Vitamin D Deficiency in Normal and Hyperandrogenic Female Rats

Vitamin D (VitD) hypovitaminosis and androgen excess (AE) are both risk factors for cardiovascular diseases in fertile women. However, the possible early interaction between AE and VitD status is not clear. Our goal was to describe how VitD status influences early changes in the biomechanical reactivity of small coronary arterioles in adult female rats after transdermal testosterone treatment. Forty-six adolescent, 90-110-gram-weighed female Wistar rats were randomly grouped into 4 groups. Twenty-four animals received an optimal VitD-supplemented diet, from which 12 animals underwent transdermal testosterone treatment. Twenty-two animals received a VitD-deficient diet, from which 11 were treated with testosterone. At 8 weeks of treatment, invasive arterial blood pressure was registered after in vivo cannulation of carotid artery. Arteriolar end and side branches (200 mu m diameter) of the left anterior descendent coronary artery (LAD) were obtained and examined with pressure arteriography in vitro. Similar segments were removed for histological examination. The inner and outer radii of the arterioles were measured using video-microscopy. Normal myogenic tone, maximal passive vasorelaxation and vasoconstriction of the arterioles were measured and statistically analyzed. The vessels' maximal smooth muscle relaxant potential, thromboxane-induced contraction capacity and normal myogenic tone were significantly influenced by actual VitD status. A lower relaxation capacity and increased wall thickness were observed in VitD-deficient groups, which could cause rigidity of the coronary arterioles and elevate cardiovascular risk. Supplementation of VitD could improve myogenic tone and relaxation and hold cardiovascular benefits.