Urinary endothelin-1 as a marker of renal damage in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) affects the kidney by acute mechanisms as well as by insidious renal medullary/papillary necrosis, resulting in tubular defects, which increase the risk of dehydration and subsequent sickle crisis. Hypoxia has been reported to stimulate endothelin-1 (ET-1) synthesis by endothelial cells and also in the renal tubule. METHODS: This case-control study measured ET-1 in urine as a marker of its renal synthesis in asymptomatic SCD patients. Baseline plasma and urinary ET-1 levels were measured and followed during a water deprivation study and a subsequent administration of desmopressin. RESULTS: Urine and plasma levels of ET-1 were elevated in patients with SCD, compared with carefully matched African-French and African controls, and urine ET-1 excretion was associated with a marked urine-concentrating defect. Moreover, urinary ET-1 output was correlated with microalbuminuria in SCD patients. CONCLUSIONS: ET-1 is known to antagonize the tubular effects of vasopressin and to promote renal scarring; increased renal production of ET-1 could produce nephrogenic diabetes insipidus and dehydration in SCD patients through a combination of fibrosis and functional resistance to vasopressin. This study provides a rationale for trials with endothelin receptor antagonists in sickle cell disease nephropathy.

Cutaneous microvascular blood flow and reactivity in patients with homozygous sickle cell anaemia.

Homozygous sickle cell anaemia (SS disease) involves a high prevalence of skin ulcerations, and background experience concerning the cutaneous microcirculatory flux and reactivity in this disease is very limited. We investigated, by laser-Doppler velocimetry, the microcirculatory cutaneous blood flow and vasoreactivity in 17 patients with SS disease but no cutaneous trophic changes, vs. the corresponding values in 18 normal matched controls. The laser-Doppler probe was placed on the foot dorsum, and recordings were made in the supine and dependent positions, and after post-ischaemic hyperaemia. The venoarteriolar reflex was calculated as the difference between the fluxes in the supine and dependent positions. In both positions, patients with SS disease exhibited clear vasodilation, with larger cutaneous fluxes than those of the controls (P=0.024 and 0.0009, respectively). The venoarteriolar reflex, expressed as a percentage of the resting supine flux, was lower in the patients (P=0.0004). These impairments of the microcirculatory fluxes, which combine a vasodilated state with abnormal vasoreactivity, resemble those observed in patients with chronic venous insufficiency and might be crucial in determining the pathogenesis of the skin ulcerations that occur in SS disease. Laser-Doppler velocimetry seems a suitable non-invasive technique for investigating such cutaneous microangiopathy.