Impairment of skin microvascular reactivity in hypertension and uraemia.

Background: Uraemia and hypertension are associated with higher risk for cardiovascular complications. Endothelial dysfunction plays an important role in the pathogenesis of cardiovascular diseases. The aim of the present study was to evaluate endothelial function in the forearm skin microcirculation of patients with essential hypertension, in hypertensive haemodialysis patients and in normotensive control subjects.
Methods: We performed laser Doppler flowmetry with iontophoresis of acetylcholine (ACh) and of sodium nitroprusside (SNP) as well as the post-occlusive reactive hyperaemia test (PORH) in 16 normal control subjects (CONT), in 16 patients with essential hypertension (EHT) and in 16 haemodialysis patients with essential hypertension (DHT). Plasma levels of endothelin-1, big-endothelin and von Willebrand factor (vWF) were also measured.
Results: The average hyperaemic response to the higher dose of ACh iontophoresis was 801+/-110% in CONT, 563+/-69 % in EHT and 308+/-64% in DHT (P<0.05, between all comparisons). Vasodilation to the higher dose of SNP was 791+/-79% in CONT, 633+/-72% in EHT and 355+/-69% in DHT (NS, P<0.001 compared with controls, respectively). The average peak flow during PORH was significantly lower in both the EHT and DHT groups compared with controls (294+/-39, 267+/-59 and 429+/-45%, respectively, P<0.05). Levels of endothelin-1, big endothelin, vWF and vWF activity were significantly higher in the DHT group (P<0.05, compared with controls).
Conclusions: In hypertensive haemodialysis patients, both endothelium-dependent and -independent vasodilation was impaired. The observed increase in plasma markers of endothelial damage indicated a progression of vascular disease.