Plasma aldosterone during extracellular fluid volume expansion in patients on regular haemodialysis

[PLASMA RENIN ACTIVITY AND ALDOSTERONE IN RENAL TRANSPLANT PATIENTS]

(Background) It has become evident in recent year that aldosterone has a pathogenic role in hypertension, heart failure and renal disease. Elevation of aldosterone occurs in a certain fraction of hemodialysis patients, and the adverse effects of hyperaldosteronism could pose a problem after kidney transplantation. Long-term effects of aldosterone level in renal transplant recipients remain unknown. (Materials and methods) All recipients underwent transplantation between 1996 and 2018 in Niigata university hospital were included in the study. Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were retrospectively analyzed in 210 recipients before and after kidney transplantation. (Results) Sixty percent of recipients had higher PRA than normal upper limit before and after transplantation. The use of angiotensin receptor blocker (ARB) or angiotensin-converting-enzyme inhibitor (ACEI) was significantly more frequent in the patients with hyperreninemia than those without one after transplantation. Sixty percent of recipients had higher PAC than normal upper limit before transplantation and it spontaneously decreased to normal level after transplantation in most of them. There was no significant correlation between PAC and blood pressure, recipient age, and renal graft function after transplantation. We divided the patients into two groups, with and without post-transplant hyperaldosteronemia. The patients with post-transplant hyperaldosteronemia (n=29) had higher diastolic blood pressure and less use of renin-angiotensin-aldosterone system (RAAS) inhibitors than those with normal PAC level. (Conclusions) The use of RAAS inhibitors should be considered in post-transplant hyperaldosteronemia patients to control blood pressure and to save their long-term renal graft and heart function.

Extrarenal renin-angiotensin systems are unable to maintain blood pressure in sheep

1. The present study was designed to assess the participation of extrarenal tissue renin-angiotensin systems (RAS) in pressure homeostasis in sheep. 2. The effect of the administration of an angiotensin II type 1 receptor antagonist (losartan; 30 mg/kg, i.v.) on mean arterial blood pressure (MABP) was investigated in eight intact (controls) and 10 binephrectomized sheep haemodialysed every 2 days for 10 days. 3. In control sheep, losartan decreased blood pressure and this decrease was significantly more marked after furosemide-induced water and salt depletion. After nephrectomy and throughout the anephric period, losartan lost its hypotensive effect, while the plasma renin concentration fell to undetectable levels. Baseline MABP became significantly lower than at the beginning of the anephric period after 7 days. The inability to maintain blood pressure after several volume-depleting haemodialysis sessions proved that an efficient system for blood pressure regulation was lacking after nephrectomy. 4. Renin gene expression measured by reverse transcription-polymerase chain reaction was found in liver, adrenal and arterial wall tissue. Neither nephrectomy nor sodium depletion enhanced this tissue renin gene expression. 5. In conclusion, the present work allows us to exclude an active role of extrarenal RAS in the maintenance of blood pressure. In addition, haemodialysis technology in nephrectomized sheep can be used as a good model for the study of extrarenal control of blood pressure.

Disorders of body fluids, sodium and potassium in chronic renal failure

A stable volume and composition of extracellular fluid are essential for normal functioning of the body. Since the kidney is primarily responsible for regulating extracellular fluid, loss of kidney function should have catastrophic consequences. Fortunately, even with loss of more than 90 percent of renal function, a remarkable capacity to regulate body fluid volumes and sodium and potassium persists. Nevertheless, this capacity is limited to chronic renal disease and this has important consequences for clinical management of these patients. How can sodium and potassium homeostasis be assessed? Methods for evaluating the steady-state regulation of sodium include measurement of body fluids and their distribution in different compartments and measurement of exchangeable and intracellular sodium. Short-term regulation of body sodium can be assessed from measurement of sodium balance during changes in dietary salt. Potassium is predominantly contained within cells and thus the assessment of its regulation requires special emphasis on measurement of steady-state body stores and potassium distribution across cell membranes. However, the methods used to make all of these measurements require assumptions that may not hold in the altered state of uremia. This raises problems in interpretation requiring critical analysis before conclusions can be made regarding sodium and potassium homeostasis in patients with chronic renal failure. This review focuses on abnormalities of body fluids, sodium and potassium in patients with creatinine clearances of less than 20 ml/min due to chronic renal failure and the impact of conservative therapy, dialysis and renal transplantation on these patients.