Plasma concentrations of 18-hydroxycorticosterone and aldosterone in continuous ambulatory peritoneal dialysis and hemodialysis patients

Plasma Levels of Adrenocortical Steroids in CAPD and Hemodialysis Patients

CAPD patients appear to have higher levels of plasma renin activity than hemodialysis patients. Increased angiotensin n may result in increased secretion of 18-OH-B and aldosterone by the adrenal zona glomerulosa.

Differences in treatment design between continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) may affect secretion of adrenocorticosteroids. Ultrafiltration during CAPD is continuous and gradual. Therefore, CAPD patients experience only minor fluctuations in extracellular fluid volume and are usually at or near their estimated dry weight (EDW). In contrast, ultrafiltration in HD patients is rapid but intermittent. Hemodialysis patients approach their EDW only at the end of each treatment period. Hemodialysis patients, therefore, may remain significantly above their EDW for prolonged periods. CAPD allows patients to liberalize their dietary intake of potassium. Some CAPD patients may require potassium supplementation (I). In contrast, HD patients may need to restrict their dietary intake of potassium to prevent potentially lethal hyperkalemia. Heparin is routinely administered during HD but not during CAPD. The present study was designed to determine if these differences in treatment design produce greater stimulation of the adrenal zona glomerulosa in CAPD than in HD patients.

Effect of aldosterone on epithelial-to-mesenchymal transition of human peritoneal mesothelial cells

BACKGROUND

Peritoneal fibrosis is one of the major causes of technical failure in patients on peritoneal dialysis. Epithelial-to-mesenchymal transition (EMT) of the peritoneum is an early and reversible mechanism of peritoneal fibrosis. Human peritoneal mesothelial cells (HPMCs) have their own renin-angiotensin-aldosterone system (RAAS), however, it has not been investigated whether aldosterone, an end-product of the RAAS, induces EMT in HPMCs, and which mechanisms are responsible for aldosterone-induced EMT.

METHODS

EMT of HPMCs was evaluated by comparing the expression of epithelial cell marker, E-cadherin, and mesenchymal cell marker, α-smooth muscle actin after stimulation with aldosterone (1-100nM) or spironolactone. Activation of extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) and generation of reactive oxygen species (ROS) were assessed by western blotting and 2',7'-dichlorofluororescein diacetate staining, respectively. The effects of MAPK inhibitors or antioxidants (N-acetyl cysteine, apocynin, and rotenone) on aldosterone-induced EMT were evaluated.

RESULTS

Aldosterone induced EMT in cultured HPMCs, and spironolactone blocked aldosterone-induced EMT. Aldosterone induced activation of both ERK1/2 and p38 MAPK from 1 hour. Either PD98059, an inhibitor of ERK1/2, or SB20358, an inhibitor of p38 MAPK, attenuated aldosterone-induced EMT. Aldosterone induced ROS in HPMCs from 5 minutes, and antioxidant treatment ameliorated aldosterone-induced EMT. N-acetyl cysteine and apocynin alleviated activation of ERK and p38 MAPK.

CONCLUSION

Aldosterone induced EMT in HPMCs by acting through the mineralocorticoid receptor. Aldosterone-induced generation of ROS followed by activation of ERK, and p38 MAPK served as one of the mechanisms of aldosterone-induced EMT of HPMCs.