AIM: The aim was to elucidate whether essential hypertension is associated with altered capillary morphology and density and to what extend exercise training can normalize these parameters.

METHODS: To investigate angiogenesis and capillary morphology in essential hypertension, muscle biopsies were obtained from m. vastus lateralis in essential hypertensive patients (n=10) and normotensive controls (n=11) before and after 8 weeks of aerobic exercise training. Morphometry was performed after transmission electron microscopy and protein levels of several angioregulatory factors were determined.

RESULTS: At baseline, capillary density and capillary-fiber-ratio were not different between the two groups. However, hypertensive patients had 9% lower capillary area (12.7±0.4 vs. 13.9±0.2μm(2) ) and tended to have thicker capillary basement membranes (399±16 vs. 358±13nm; P=0.094) than controls. Protein expression of vascular endothelial growth factor (VEGF), VEGF receptor-2 and thrombospondin-1 were similar in normo- and hypertensive subjects but tissue inhibitor of matrix metalloproteinase was 69% lower in the hypertensive group. After training, angiogenesis was evident by 15% increased capillary-to-fiber ratio in the hypertensive patients only. Capillary area and capillary lumen area were increased by 7% and 15% in the hypertensive patients whereas capillary basement membrane thickness was decreased by 17%. VEGF expression after training was increased in both groups whereas VEGF receptor-2 was decreased by 25% in the hypertensive patients.

CONCLUSION: Essential hypertension is associated with decreased lumen area and a tendency for increased basement membrane thickening in capillaries of skeletal muscle. Exercise training appears to improve the diffusion conditions in essential hypertension by altering capillary structure and capillary number. This article is protected by copyright. All rights reserved.