Regulation of plasma aldosterone in anephric and non-nephrectomized patients during hemodialysis treatment

Regulation of Plasma Aldosterone during Hemodialysis

In order to clarify the influence of serum potassium, serum sodium and plasma angiotensin II concentrations on aldosterone release during hemodialysis (HD), six chronic hemodialysis patients were studied during HD with varying dialysate sodium concentrations and different buffers. Plasma aldosterone concentrations were higher during acetate than bicarbonate HD, during low sodium compared to high sodium HD, and were correlated inversely to serum sodium concentrations. The decline in plasma aldosterone concentrations during HD paralleled the decrease in serum potassium concentrations, and plasma aldosterone concentrations were correlated with serum potassium concentrations. In addition, plasma aldosterone and plasma angiotensin II concentrations were correlated significantly. It is proposed that serum potassium and the renin-angiotensin system are the main factors of aldosterone release during hemodialysis, while serum sodium per se seems to be of less importance. The dialysate buffer employed also plays a role in aldosterone regulation (via the renin-angiotensin system)

Effect of spironolactone on K(+) homeostasis and ENaC expression in lymphocytes from chronic hemodialysis patients

BACKGROUND

Cardiac disease is the major cause of death in hemodialysis patients (HD). It is now clear that aldosterone has deleterious effects in the cardiovascular system. In the present study, we evaluated the effects of an aldosterone-antagonist, spironolactone, on the extrarenal regulation of potassium in HD patients. Furthermore, to validate the effectiveness of the spironolactone dose-design, we measured the expression of Na(+)-channel (ENaC alpha subunit) in peripheral blood mononuclear cells (PBMC), before and after a two-week course of spironolactone.

METHODS

The study design included a two-week baseline period, followed by spironolactone treatment (50 mg three times weekly for 15 days), and by a two-week washout period and then a two-week placebo period. An oral K(+) load (0.3 mEq/K(+) kg body weight plus carbohydrates) was administered at the end of each period, and time-course of plasma potassium was evaluated. ENaC expression in PBMC was assessed before and after spironolactone.

RESULTS

The maximal increase in plasma potassium after the K(+) carbohydrate load was: control 5.33 +/- 0.88 mEq K(+)/L; spironolactone 5.23 +/- 0.68 mEq K(+)/L; placebo 5.38 +/- 0.61 mEq K(+)/L (N= 9). No patients developed hyperkalemia during the spironolactone treatment period. ENaC expression was significantly higher in all six HD patients studied, compared to control subjects (P < 0.05). Treatment with spironolactone in HD patients reduced alpha subunit mRNA expression to values similar to those of normal subjects.

CONCLUSION

Spironolactone may be considered for the treatment of selected chronic HD patients. The effect of the drug on a known target of aldosterone, the ENaC, demonstrates the effectiveness of the drug to block aldosterone effects in nonepithelial tissues.