Morphometry of the small arteries and arterioles in the rat heart: effects of chronic hypertension and exercise

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Abstract
Study objective – The aim of the study was to characterise small coronary arteries and arterioles quantitatively in rat left ventricle and septum under various experimental conditions. Design – Morphometric analysis of resistance vessels was carried out in rats divided into four experimental groups: (1) control animals sedentary; (2) control animals exercised (moderate swimming); (3) renal hypertensive animals sedentary; (4) renal hypertensive rats exercised. Hypertensive animals received the two kidney/one clip Goldblatt procedure; control animals were sham operated. Subjects – Experimental animals were 28 female Sprague-Dawley rats. Measurements and results – In hypertensive rats, there was a significant increase in left ventricular mass and a reduced coronary reserve. Morphometric analysis of 10 000 resistance vessels in the coronary bed showed that cardiac hypertrophy in hypertensive rats was characterised by increased wall thickness in arterioles and small arteries and an increased lumen to wall ratio, particularly in vessels of 30-100 μm size. The number of capillary profiles per arteriole in cross section was also decreased in the hypertensive rat. Chronic exercise increased the number of capillaries per arteriole in controls but not in hypertensive rats. Swimming did not affect the architecture of the resistance vessels. Conclusions – Chronic renal hypertension, but not swimming, produces subtle but significant changes in structure of coronary resistance vessels.