Reduction of Tissue Na⁺ Accumulation After Renal Transplantation

Chronic kidney disease (CKD) engenders salt-sensitive hypertension. Whether or not tissue Na⁺ accumulation is increased in CKD patients remains uncertain. How tissue Na⁺ is affected after renal transplantation has not been assessed.

We measured tissue Na⁺ amount in 31 CKD patients (stage 5) and prospectively evaluated tissue Na⁺ content at 3 and 6 months, following living-donor kidney transplantation. Additionally, pre- and post-transplantation data were compared to 31 age- and sex-matched control subjects. ²³Na-magnetic resonance imaging (²³Na-MRI) was used to quantify muscle and skin Na⁺ of the lower leg and water distribution was assessed by bioimpedance spectroscopy.

Compared to control subjects, CKD patients showed increased muscle (20.7 ± 5.0 vs. 15.5 ± 1.8 arbitrary units [a.u.], P < 0.001) and skin Na⁺ content (21.4 ± 7.7 vs. 15.0 ± 2.3 a.u., P < 0.001), whereas plasma Na⁺ concentration did not differ between groups. Restoration of kidney function by successful renal transplantation was accompanied by mobilization of tissue Na⁺ from muscle (20.7 ± 5.0 vs. 16.8 ± 2.8 a.u., P < 0.001) and skin tissue (21.4 ± 7.7 vs. 16.8 ± 5.2 a.u., P < 0.001). The reduction of tissue Na⁺ after transplantation was associated with improved renal function, normalization of blood pressure as well as an increase in lymphatic growth-factor concentration (vascular endothelial growth factor C [VEGF-C] 4.5 ± 1.8 vs. 6.7 ± 2.7 ng/ml, P < 0.01).

Tissue Na⁺ accumulation in predialysis patients with CKD was almost completely reversed to the level of healthy controls after successful kidney transplantation.