Regulation of plasma aldosterone concentration in anephric man and renal transplant recipients

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.

Disordered aldosterone-volume relationship in end-stage kidney disease

INTRODUCTION

Sodium loading, and subsequent volume expansion, suppresses aldosterone levels in individuals with normal renal function. We hypothesised that loss of renal function impairs this volume-aldosterone relationship.

MATERIALS AND METHODS

With multifrequency bioimpedance spectroscopy, we measured total body water (TBW), extracellular volume (ECV), and intracellular volume in five haemodialysis patients at varied states of hydration and in five healthy volunteers during low-, normal-, and high-salt diets. Serum aldosterone, potassium, and C-reactive protein were measured simultaneously. Scatterplots and general estimating equations were used to examine the relationship among these variables.

RESULTS

In healthy volunteers with salt loading, and in haemodialysis subjects with increased inter-dialytic weight gain, expansion of ECV led to reciprocal declines in serum aldosterone concentrations. The relationship was more profound in healthy volunteers (p<0.001) than in haemodialysis subjects (p=0.1). Notably, haemodialysis subjects posted consistently higher levels of ECV (median 49.6% TBW, IQR 43.9-51.8% compared to 41.1%, 39.9-42.8% in volunteers) and serum aldosterone (median 26.7 ng/dl, IQR 19.8-29.6 compared to 12.4 ng/dl, 8.8-16.0 in volunteers). Serum potassium did not appear to influence aldosterone concentration (p=0.9).

CONCLUSIONS

The shift of the volume-aldosterone curve in haemodialysis subjects suggests that end-stage kidney disease is a state of high volume and inappropriately high aldosterone. These data have important clinical implications, as dialysis patients may benefit from both volume reduction and mineralocorticoid receptor blockade.

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

The relationships between plasma aldosterone and changes in plasma potassium, plasma cortisol, plasma sodium, blood volume and body weight have been studied in 6 anephric and 11 non-nephrectomized patients on regular hemodialysis. In all patients, the plasma aldosterone concentration decreased during dialysis. In the anephric patients, a significant correlation (p less than 0.001) was demonstrated between the fall in plasma aldosterone and the fall in plasma potassium (total body potassium depletion). Measurements between consecutive hemodialyses, furthermore, showed a significant correlation (p less than 0.001) in anephric patients between total body potassium repletion (increasing plasma potassium) and the rise in plasma aldosterone. In contrast, the potassium and aldosterone changes did not correlate in the non-nephrectomized group. During dialysis, a decrease was found in all parameters, but no correlation was demonstrable in either group between the changes in plasma aldosterone and the fall in plasma cortisol, sodium, blood volume and body weight. The data in the anephric patients emphasize the important role of potassium in the regulation of aldosterone secretion.

The renin-aldosterone system and renal hemodynamics in patients with posttransplant hypertension

Plasma renin concentration (PRC), plasma aldosterone concentration (PAC), renal plasma flow (RPF) and glomerular filtration rate (GFR) have been studied in 19 patients who had received a renal allotransplant. Group 1 consisted of 7 normotensive and group 2 of 12 hypertensive patients. Bilateral nephrectomy was performed in all patients; all were on a fixed daily sodium intake, and no antihypertensive agents were given. No significant differences were found between the groups in age, time after transplantation or dosages of prednisone. PRC and PAC were normal in all but one patient in group 1 and two in group 2. In these three patients a slight elevation of PRC was measured. After one hour in the erect position, a significant increase was measured in PAC, but not in PRC in both groups. After 6 days on a 10 mEq sodium diet, PRC and PAC increased significantly in both groups. After a further 6 days on the diet plus 150 mEq sodium daily, significant decreases in PRC and PAC were measured in both groups. No differences were detected in PRC or PAC between groups 1 and 2 either before or after the two dietary periods. RPF was significantly lower in the hypertensive group, whereas no significant difference was found in GFR between the groups. No significant relationship could be demonstrated between blood pressure (BP) and PRC or PAC, and PRC and PAC were not correlated to each other. RPF was significantly correlated to mean BP and PRC in the normotensive group but not in the hypertensive. It is concluded that PRC and PAC are normal in most patients with posttransplant hypertension, whereas the RPF is decreased. It is suggested that an abnormal regulation of renin secretion plays a role in the sustained elevation of BP after renal allotransplantation.

Haemodynamic effects of prenalterol in patients on dialysis

Haemodialysis hypotension occurs with particular frequency in bilateral nephrectomised patients. This reflects the importance of the renin-angiotensin-aldosterone system for maintaining normal blood pressure. Failure of vascular access (due to clotting and thrombosis of shunts) and ischaemic necrosis of transplanted kidneys in hypotensive patients prompted us to treat them orally with a new beta 1-adrenergic agent (prenalterol). Blood pressure was normalised in 4 out of 5 patients. Because of delayed renal elimination of the drug, daily dosage must be reduced to prevent symptoms of adrenergic stimulation. A study of the pharmacokinetics of prenalterol in uraemia is in preparation.

The adrenocortical response to angiotensin II infusion in anephric and non-nephrectomized patients on regular hemodialysis

In the present study 8 anephric and 4 non-nephrectomized patients were stimulated with angiotensin II (A-II). In 5 of the anephric patients, an increased plasma aldosterone concentration (PAC) in response to ACTH stimulation had previously been demonstrated. After A-II stimulation, all 8 anephric patients responded with a significant rise in PAC although the increase was less pronounced than in 4 non-nephrectomized patients. In both groups of patients the increase in PAC was correlated to the increase in diastolic and systolic BP and to the A-II dose. Furthermore, in the non-nephrectomized patients, the plasma renin activity showed a significant decline, which was inversely correlated to the increase in PAC. When all 12 patients, regardless of the difference in remaining renin-angiotensin system, were considered as one population, the variable basal levels of PAC correlated significantly to the increase in PAC during A-II and ACTH stimulation. It is concluded that the adrenals of anephric man respond to A-II with an increase in PAC and that the reason for a lower response appears to be the lack of the renin-angiotensin system.

Augmented aldosterone and insulin responses to potassium infusion in dogs with renal failure

The present study examines acute potassium-induced insulin and aldosterone responses in renal failure, and the role of chronic dietary potassium intake in modifying these acute responses. Plasma aldosterone (PA) and insulin (IRI) responses to acute KCl infusion were examined in control and remnant kidney dogs on two potassium intakes. Dogs (N = 8) received the KCl infusions after 10 days of a 60, and then 10 days of a 200, mEq daily potassium intake during control and after surgical-induced renal failure (CRF). A one hour intravenous infusion of KCl (2 mEq KCl/kg/hr) in dextrose and water was performed with blood samples for PA, IRI, creatinine and electrolytes, and urine for electrolytes and creatinine at 20 minute intervals one hour preceding, during, and after the infusion. Preinfusion PA was higher (P less than 0.05) in controls and CRF dogs on 200 mEq potassium intake compared to 60 mEq potassium intake. The peak incremental responses of PA to KCl infusion were increased (P less than 0.01) in CRF compared to controls on 60 mEq (PA 36 +/- 4.2 vs. 26 +/- 3.0 ng/dl) and 200 mEq (delta PA 49 +/- 5.6 vs. 37 +/- 2.8 ng/dl) potassium intakes. Differences in incremental PA responses in CRF were not due to altered aldosterone metabolic clearance rates, changes in renin, or ACTH activity. Pre-infusion IRI was higher (P less than 0.05) in CRF than control dogs on both potassium diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertension and kidney transplantation

Patients with kidney transplants are often hypertensive. Investigators have described the characteristics of this hypertension in man. Moreover, the hypertension of kidney transplant patients has a higher probability of being responsive to surgical intervention than does hypertension in the general population. Yet the mechanisms of the many varieties of posttransplantation hypertension are not known in detail. Detailed studies that would best be done in animal models are rare. Both medical and surgical management of this transplantation-associated complication needs further study.

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

This study explores the hypothesis that the continuous ultrafiltration that accompanies continuous ambulatory peritoneal dialysis (CAPD) produces greater activation of the renin-angiotensin aldosterone axis than does the intermittent ultrafiltration that accompanies thrice weekly hemodialysis (HD). Plasma renin activity (PRA), active renin (AR), total renin (TR), inactive renin (IR), 18-hydroxycorticosterone (18-OH-B), aldosterone (PAC), and cortisol were measured in plasma from CAPD (n = 6) and HD (n = 10) patients. Blood from CAPD patients was sampled at 8 AM after overnight recumbency and at 12 noon after four hours ambulation. Blood from HD patients was sampled immediately pre-HD (8 AM) and post-HD (12 noon) at both 8 AM and 12 noon. PRA (P less than 0.01), AR (P less than 0.01), and AR/TR (100%; P less than 0.01) were higher in CAPD than in HD. IR and TR were not different in the two groups. Plasma 18-OH-B was normal in HD but markedly elevated in CAPD. 18-OH-B was higher in CAPD than in HD at 8 AM (P less than 0.05) and at 12 noon (P less than 0.05). Plasma cortisol was not different in the two groups. We conclude that the greater degree of renin activation in CAPD versus HD contributes to the higher levels of 18-OH-B and PAC observed in CAPD patients.

Hormonal responses to acute volume changes in anephric subjects

The response of plasma aldosterone and cortisol concentrations to acute volume depletion was studied in 18 chronically anephric subjects and four recently nephrectomized subjects. Volume-depleting hemodialysis and hemodialysis without volume depletion produced insignificant changes in plasma aldosterone concentrations in chronically anephric subjects. Failure of volume depletion to increase plasma aldosterone concentrations in these subjects could not be attributed to reductions in plasma potassium concentrations and was in marked contrast to the effect on plasma cortisol concentrations, which increased significantly during volume depletion. Changes in plasma cortisol concentrations exhibited a negative correlation with changes in diastolic blood pressure (r = -0.712, P less than 0.001) and were shown to correspond to similar changes in plasma ACTH concentrations. Comparable increases in plasma cortisol and ACTH concentrations were also demonstrated in the studies on recently nephrectomized subjects, who, in contrast to chronically anephric subjects, exhibited increases in plasma aldosterone concentrations which were concordant with the changes in plasma cortisol and ACTH concentrations. These findings suggest that plasma aldosterone concentrations are regulated by a volume-sensitive mechanism in recently nephrectomized subjects but not in chronically anephric subjects. We interpret these data as evidence of aldosterone responsiveness to ACTH that persists for a limited time only after removal of the stimulus provided by the renin-angiotensin system. Volume-related changes in plasma cortisol and ACTH concentrations occur in the absence of stimulation by a functioning renin-angiotensin system.

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.

Extrarenal prorenin and renin in anephric patients

Active renin was detected in 6 of 7 anephric patients (mean value: 0.72 +/- 0.27 microU/ml, n = 7; normals: 19.7 +/- 2.4 microU/ml, n = 10), using an assay method without intrinsic acid- or cryoactivation. Prorenin, measured as the difference between plasma renin concentration (PRC) before and after acid-activation in vitro, was present in considerable amounts in all patients (32.4 +/- 3.5 microU/ml; normals: 80.7 +/- 9.7 microU/ml). PRC after cryoactivation at--5 degrees C during 1 week was insignificantly lower than after acid-activation in the patients. There was a linear correlation between PRC after either activation procedure (p less than 0.01). Supine or upright posture did not influence active or inactive renin in the anephric subjects. Our studies show that low but significant levels of active renin and a considerable amount of prorenin are detectable in anephric patients. The data suggest that prorenin in normal subjects in a significant proportion is of extrarenal origin. Orthostasis has no effect on extrarenal active or inactive renin.

Adrenergic modulation of extrarenal potassium disposal

We studied the role of catecholamines in the regulation of potassium homeostasis in nine healthy subjects given intravenous potassium chloride (0.5 meq per kilogram of body weight) in the presence and absence of propranolol. Potassium infusion elevated serum potassium 0.6 +/- 0.09 meq per liter (mean +/-S.E.M.). Addition of propranolol augmented the rise (0.9 +/- 0.05 meq per liter) and prolonged the elevation in serum potassium without decreasing urinary potassium excretion. In a separate study, the same potassium load was administered with a concomitant infusion of epinephrine in five subjects. Epinephrine markedly blunted the increment in serum potassium (0.1 +/- 0.06 meq per liter) while reducing renal potassium excretion. Plasma aldosterone was not altered by the experimental procedures. Serum insulin fell minimally in the presence of propranolol but was unaffected by epinephrine. beta-Adrenergic blockade impairs and epinephrine enhances extrarenal disposal of an acute potassium load. These findings suggest that in patients with impaired potassium disposal, the risk of hyperkalemia may be increased when sympathetic blockade is induced.

Dissociation of the diurnal variation of aldosterone and cortisol in anephric subjects

Diurnal variation of plasma aldosterone and cortisol concentration in man was studied in 13 anephric subjects and 7 normal subjects. All subjects were ambulatory and active throughout the study except during an 8-hour sleep period. Six anephric subjects received Kayexalate (sodium polystyrene sulfonate) during the studies to prevent potassium accumulation and increase in plasma potassium concentration. Diurnal variation of plasma aldosterone concentration with peak and nadir concentrations at 12:00 noon and 12:00 midnight respectively was demonstrated in the studies on normal subjects. Changes in plasma aldosterone concentration were not significantly correlated with changes in plasma concentration but were highly correlated with changes in PRA (P less than 0.001). There was a highly significant correlation between plasma aldosterone and potassium concentration in the anephric subjects studied without Kayexalate administration (P less than 0.001). In the anephric subjects who received Kayexalate, plasma aldosterone and potassium concentration remained stable, and no correlation could be demonstrated. No diurnal variation of plasma aldosterone concentration could be demonstrated in either group of anephric subjects, whereas plasma cortisol concentration varied as in the studies on normal subjects. Conclusion. Diurnal variation of plasma aldosterone concentration is dependent on continued stimulation by the renin-angiotensin system. Loss of this stimulation has no demonstrable effect on the diurnal variation of plasma cortisol concentration.

The substitutive role of ACTH in supporting aldosterone response to head-up tilt during acute renin suppression in patients with essential hypertension

The relative contribution of the renin-angiotensin system, adenocorticotrophic hormone (ACTH) and plasma electrolytes in the response of plasma aldosterone to 30 minutes of 65 degrees head-up tilt was assessed in 10 essential hypertensive patients. Studies were carried out before and during acute blockade of renin release by propranolol, ACTH suppression by dexamethasone and combined renin and ACTH blockade. In control studies orthostasis induced significant increases only in plasma renin activity and aldosterone. In contrast, when the renin response to tilt was acutely suppressed by propranolol administration, the aldosterone response was nonetheless maintained but now appeared to be under ACTH control, since concurrent increases in cortisol were observed. During ACTH suppression aldosterone increased during tilt and so did renin. However, during combined ACTH and renin blockade aldosterone failed to increase during tilt. These studies suggest that the aldosterone secretory response to head-up tilt is normally mediated by the renin-angiotensin system but, when the renin response is suppressed, an ACTH response is elicited which assumes a backup role. However, when these two systems are blocked other factors appear unable to respond during tilt to support a normal aldosterone response.

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

The influence of extracellular fluid volume expansion on the plasma aldosterone concentration (PAC) was investigated in five anephric and six non-nephrectomized patients on regular haemodialysis, and compared to a control group of four anephric and four non-nephrectomized patients. Plasma-renin activity, cortisol, Na+, and K+ were measured together with the PAC during the investigation. In anephric patients the PAC remained constant during the control period as well as during extracellular fluid volume expansion by infusion of 350 mmol of 20% mannitol. In the non-nephrectomized patients PAC diminished after mannitol infusion. The decline in PAC was correlated with the basal levels of PAC and the plasma renin activity. It is concluded that 5% extracellular fluid volume expansion has no direct influence on the regulation of PAC in patients without the renal renin-angiotensin system and that the regulation of PAC in anephric patients in the present investigation is probably mediated by changes in potassium and ACTH.

The effect of severe trauma on urinary cyclic AMP in children of different ages

Under routine clinical conditions the urinary excretion of cyclic AMP was studied in 97 healthy children (3 months to 16 years old) and 65 child victims of various forms of trauma and proved to be age-dependent. The mean admission cAMP urinry levels for children of all ages were increased by 44.8% and were time dependent. In 26 injured children (3 months to 9.5 years old) the excretion increased to 12.10 +/-1.29 mumol cAMP/g creatinine as compared to 8.06 +/- 2.25 mumol cAMP/g crEAtinine (50.0%; P less than 0.01) and in 38 children (9.5-16 years) it rose to 6.43 +/- 4.12 from 4.72 mumol +/- 1.10 (36.2%; P less than 0.001). In 23 victims admitted within the first two hours after trauma the cAMP levels were elevated by 31.25% in contrast to 49.2% elevation in those admitted from 2 to 24 h after trauma. In a five-day follow-up of a group of 15 surviving patients the highest excretion of cAMP was found on the first day. It was followed by a steep decline until the values plateaued on the third day at values slightly elevated above control. Compared with the fifth day, the first day excretion expressed as mumol cAMP/24 h was enhanced by 92.3% (P less than 0.01) and as a ratio to creatinine (muol/g creatine) by 52.24% (P less than 0.05. In comparison with injured adults studied previously under analogical conditions, the cAMP excretory response to trauma in children differs in higher intensity (P less than 0.01) and in the nature of the daily pattern starting with the third day. It is pointed out that the intensity of the cAMP response to pathological stimuli may be age-dependent also in other clinical conditions.

Arterial and venous angiotensin II in normal subjects. Relation to plasma renin activity and plasma aldosterone concentration, and response to posture and volume changes

Plasma renin activity, arterial and venous angiotensin II (A II) concentrations, and plasma aldosterone concentration were measured in 16 normal subjects (mean age = 34 years) after 8 hours of recumbency, following 2 hours of ambulation, and again 30 minutes after administration of furosemide intravenously. Measurements were obtained during periods of sodium restriction and again during sodium surfeit. Both arterial and venous A II exhibited a 3-fold increase from low values of 8.8 +/- 2.5 and 8.6 +/- 2.5 pg/ml of plasma, respectively, during recumbency on high sodium intake to values of 23.9 +/- 4.1 and 26.5 +/- 6.2 pg/ml, respectively, following intravenous furosemide during sodium restriction. Corresponding values for aldosterone exhibited a 5-fold rise from 5.6 ng/100 ml to 32.0 ng/100 ml, whereas plasma renin activity (PRA) measured by an in vitro assay exhibited a 20-fold rise from 0.6 +/- 0.2 ng of angiotensin I (AI) generated per ml per hour to 13.1 ng/ml per hour. Despite the disparity in the magnitude of these increases, significant correlations were identified between all four of the measured parameters, indicating a major role of the renin-angiotensin system in regulating aldosterone output in response to volume and posture-related stimuli. Values of arterial and venous immunoreactive A II were closely correlated ( r = +0.72, P less than 0.005), but significant differences were demonstrated between low and high salt periods, suggesting that changes in metabolism of A II in the peripheral circulation may occur during sodium restriction.

Control of renin release: a review of experimental evidence and clinical implications

Present knowledge of the mechanisms regulating release of renin is reviewed with particular emphasis on neural factors. Evidence is given for a direct effect of renal innervation on beta adrenergic receptors in juxtaglomerular cells, and for the involvement of reflex release of renin in conditions such as tilting and acute salt depletion. Participation of neural and nonneural mechanisms of control is also shown to occur in other conditions, such as aortic constriction and hemorrhage. The view is held that neural sympathetic factors might explain some of the renin disturbances found in essential hypertension. First, in patients with high renin hypertension part of the hypertension is renin-dependent, and these pressor levels of renin seem to be neurally induced since they can commonly be suppressed by beta adrenoreceptor blocking agents. Second, the hypothesis is presented that patients with low renin hypertension, at least those who have no volume disturbance, have a blunted sympathetic control of renin release. Therefore a sufficiently precise test of sympathetic activity, and possibly of body fluid volumes, should be associated with renin profiles for a better understanding of the pathophysiology of arterial hypertension and as a better guide to therapeutic management. Indeed, most of the available antihypertensive drugs act on sympathetic activity, body fluid volume or renin, and this multifaceted profile would provide more rational guidelines for treatment.

Paradoxical glucose-induced hyperkalemia. Combined aldosterone-insulin deficiency

Severe hyperkalemia associated with spontaneous hyperglycemia as well as with the intravenous infusions of glucose occurred in an insulin-requiring diabetic patient in the absence of potassium administration, the use of diuretics which inhibit urinary potassium excretion or acidemia. Metabolic balance studies revealed, in addition to diabets, the presence of isolated aldosterone deficiency of the hyporeninemic type. Intravenous glucose infusions (0.5 g/kg body weight) produced significant hyperkalemia but desoxycortisone acetate (DOCA) therapy (10 mg/day) prevented the glucose-induced hyperkalemia. In this patient, the serum potassium concentration increases after the intravenous infusions of glucose because there is insufficient aldosterone and insulin to reverse the transfer of potassium to the extracellular fluid which normally occurs after hypertonic infusions of glucose. Although DOCA replacement modifies the distribution of potassium in the extracellular fluid and blunts the hyperkalemic effect of intravenous infusions of glucose, a rise in the insulin level is required for the usual hypokalemic response to intravenously administered glucose. These studies illustrate the risk of raising blood glucose levels in patients with combined aldosterone and insulin deficiency and the tendency towards hyperkalemia in diabetic patients under certain clinical conditions.

Control of plasma aldosterone in normal man during upright posture

Plasma aldosterone, plasma renin activity (PRA), plasma cortisol as parameter of ACTH activity and the serum concentrations of sodium and potassium were determined at short time intervals in 10 healthy students after an overnight bedrest and during three hours of ambulation. While PRA rose significantly within 15 minutes of orthostasis in all students, plasma aldosterone showed a similar rapid increase in some of the subjects only. These persons demonstrated also a simultaneous increase of serum potassium or of plasma cortisol. Plasma aldosterone rose not before 30 to 60 minutes after change to the upright position in subjects who showed neigher plasma cortisol nor serum potassium increases. It is concluded that the immediate rise of plasma aldosterone during orthostasis seems to depend on a stimulation by ACTH of by potassium. The main stimulus of plasma aldosterone during orthostasis appears to be the renin angiotensin system. If the aldosterone response to posture is mediated only through this system a delay of 30 to 60 minutes is observed.

The effect of potassium loading on sodium excretion and plasma renin activity in Addisonian man

Potassium has been shown to suppress plasma renin activity (PRA). This study was designed to study the role of increased aldosterone production in the mediation of such a response. Five patients with adrenal insufficiency were placed on a diet of 60 meq potassium and 100-150 meq of sodium while receiving a constant amount of cortisone acetate and Florinef. Upright PRA was determined each day for 2-3 days in the control period and then for 3-4 days after potassium intake had been increased to 200-300 meq/day. Potassium loading induced a natriuresis. Hence, patients were either sodium replaced (six studies in four patients) or allowed to become sodium depleted (three patients). Potassium loading without replacement was associated with a decrease in weight, negative sodium balance, hyperkalemia, and a positive potassium balance. PRA rose during the experimental period. Potassium loading with sodium replacement was associated with little change in weight or sodium balance. Hyperkalemia and positive potassium balance were present to the same degree as found in the studies without sodium replacement. When all PRA values are considered (both morning and evening values) there was no significant change with potassium loading (+ 1.31 ng/ml per h; range + 6.9 to -2.0). We conclude that hyperkalemia or a positive potassium balance did not suppress PRA in Addisonian man in these studies when sodium balance was maintained, nor did it prevent a rise in PRA when sodium balance was negative.

Hypertension due to renal artery stenosis in transplanted kidneys

Hypertension appeared to be related to stenosis of the hypogastricrenal artery system in 5 patients among 153 recipients of renal allografts. Renin assay and arteriography were crucial in the comprehensive evaluation of patients whose hypertension was not clearly related to rejection or excessive sodium intake. Hypereninemia was persistent in 4 of the 5 patients. Stenoses of the transplant renal arteries in three patients were caused by extensive intimal plaque formation. In one patient, periarterial fibrosis caused reduction of flow; 180 degrees torsion of the anastomosis resulted in stenosis in the fifth patient. Surgical correction is difficult and may be facilitated by a transabdominal approach. Vein bypass is probably preferable to patch angioplasty for intimal lesions. Following operation, hypertension was ameliorated and function improved in all patients. Rejection, which has been suggested as one of the causes of intimal plaque formation, ultimately led to the loss of the transplant in one patient. Function is normal in two patients; two patients have evidence of chronic rejection. No effort should be spared to evaluate this special group of patients whose transplant function can predictably be prolonged by decisive surgical management.

Control of aldosterone responsiveness in terminal renal failure

Control of aldosterone responsiveness in terminal renal failure. Plasma aldosterone concentration in 30 hemodialysis patients correlated closely with renin concentration, renin activity or renin and potassium concentrations combined (r is greater than or equal to 0.62; P is less than 0.01), and increased consistently in response to upright posture or corticotropin administration. Aldosterone response to hemodialysis was variable. Significant correlations (r is greater than or equal to 0.65; P is less than 0.01) were demonstrated between postural plasma aldosterone and renin responses, between aldosterone responses to corticotropin and basal plasma aldosterone or renin and potassium values, between hemodialysis-induced changes in plasma aldosterone and those in potassium or renin; but not between various indexes of heparin treatment and aldosterone activity. Bilateral nephrectomy reduced basal plasma renin and aldosterone concentrations and aldosterone responsiveness in five preoperatively normoreninemic or hyperreninemic patients, but not in a hyporeninemic patient. These results demonstrate the complementary roles of circulating renin and potassium in the control of aldosterone release under basal and stimulatory conditions in patients with terminal renal failure. Administration of heparin in dosages used during long-term hemodialysis does not appear to significantly interfere with aldosterone control.

Modulation of plasma aldosterone concentration by plasma potassium in anephric man in the absence of a change in potassium balance

In studies on seven anephric patients, glucose and insulin administration before hemodialysis produced a significant reduction in plasma potassium concentration (mean reduction = 1.3, 1.7, and 1.4 meq/liter at 60, 120, and 180 min, respectively) which was accompanied by a significant and sustained reduction in plasma aldosterone concentration. There was a significant correlation between plasma aldosterone and plasma potassium concentration (r = +0.74, P < 0.001) and between changes in the concentration of plasma aldosterone occurring in individual patients and the corresponding changes in plasma potassium concentration (r = +0.52, P < 0.01). There was no significant change in plasma sodium concentration, and plasma corticoid concentration, which was monitored as an index of ACTH elaboration, was reduced at 60 min but increased subsequently as symptoms attributable to hypoglycemia were observed. These studies demonstrate that plasma aldosterone concentration can be modulated acutely by transitory changes in plasma potassium concentration without a change in potassium balance. The effect of glucose and insulin administration on intracellular potassium in the adrenal cortex is uncertain, and although increased net movement of potassium into cells is the presumptive mechanism of the reduction in plasma potassium concentration, whether the potassium content of the adrenal cortex may have increased or decreased or remained essentially unchanged, cannot be inferred from our data.

Relative influence of acute sodium and volume depletion on aldosterone secretion in nephrectomized man

Plasma aldosterone concentration can increase in anephric man during hemodialysis despite the lack of kidneys to produce renin. Because the metabolic clearance rate of aldosterone does not change during hemodialysis, aldosterone secretion must increase in response to sodium depletion, volume depletion, or both. This study was designed to determine the relative influence of sodium and volume depletion by ultrafiltration and hemodialysis on plasma aldosterone concentration in anephric man. Fluid (547 ml) was removed from 13 anephric subjects during 4 hours of ultrafiltration in the absence of hemodialysis. Plasma sodium and potassium concentration did not change during ultrafiltration, but total body sodium and potassium decreased. Plasma aldosterone concentration did not change significantly. Each subject was then hemodialyzed for 8 hours. In 5 subjects, an additional liter of fluid was removed without a significant change in plasma sodium concentration. Plasma aldosterone concentration also did not change in response to the reduction in fluid volume. In 8 subjects, an additional liter of fluid was removed, and plasma sodium concentration decreased from 138.5 to 130.0 mEq/liter. Plasma aldosterone concentration increased from 8.3 to 19.6 ng/100 ml plasma. Three additional anephric subjects were hemodialyzed against a dialysate containing 125.0 mEq sodium/liter for 8 hours. Plasma potassium and total body fluid volume were held constant. Plasma sodium concentration decreased from 138.5 to 125.0 mEq/liter, and plasma aldosterone concentration increased from 7.4 to 24.3 ng/100 ml plasma. These data indicate that acute sodium depletion by hemodialysis accompanied by decreased plasma sodium concentration without a change in plasma potassium concentration or fluid volume can stimulate aldosterone secretion independently of the renal renin-angiotensin system.