Influence of acute stimuli on plasma aldosterone concentration in anephric man and kidney allograft recipients

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 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.

Lack of prolactin involvement in corticosteroid secretion

In mammals prolactin can modify adrenal steroidogenesis. Its trophic effect on adrenal cells where prolactin receptors have been identified suggest a direct impact upon corticosteroid biosynthesis. In man, this role of prolactin remains controversial. The purpose of our study was to investigate the effects of chronic hyperprolactinemia on basal and stimulated corticosteroid hormone secretion. Seven women with untreated chronic hyperprolactinemia (HPRL) were included in the study. In each of them, a beta 1-24 ACTH test was performed on a normal and low Na+ diet for 4 days. Basal and ACTH-stimulated cortisol, aldosterone, deoxycorticosterone and 17 hydroxyprogesterone secretion were not significantly different in HPRL and NPRL women. These results do not support evidence for any significant role of prolactin upon corticosteroid biosynthesis in man. They also suggest that prolactin is not the pituitary factor which modulates ACTH or low Na+ diet stimulated corticosteroid secretion.

A highly sensitive cytochemical bioassay for plasma angiotensin II

A highly sensitive cytochemical bioassay has been developed for measuring angiotensin II in human plasma. The assay depends on the ability of angiotensin II to alter the reducing potency of the zona glomerulosa as measured by Prussian blue staining and microdensitometry. An inverse correlation between the intensity of the stain and the logarithm of concentration existed over the range 0.05-5.0 fmol/1 of angiotensin II. The limit of sensitivity of the assay in plasma was 50 fmol/1; the index of precision was 0.07 +/- 0.04 (mean +/- SD; n = 15); and the coefficient of variation of a quality control sample was 34%. The response was specific for angiotensin II; approximately 10(2) times more angiotensin III and approximately 10(6) times more ACTH was required to produce a similar effect. Angiotensin I had no significant activity. A significant inverse relationship existed between sodium intake and bioactive angiotensin II in 5 normal subjects studied on low, normal and high sodium diets. Extremely low levels of angiotensin II were detected in anephric subjects.

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.

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.

Responsiveness of plasma aldosterone: dependency upon basal secretory activity

The responsiveness of plasma aldosterone levels to various stimuli was evaluated in 44 normal subjects, 17 patients with mild to moderate renal failure, 30 patients with terminal renal failure, and 13 anephric subjects. Plasma aldosterone, renin activity (PRA), cortisol, sodium, and potassium levels were measured before and after one hour of upright posture (N = 191); ACTH infusions (N = 76); and angiotensin II infusion (N = 36). Plasma aldosterone responses correlated (r greater than or equal to 0.53; p less than 0.02) with basal plasma aldosterone levels during upright posture in all four groups, with ACTH infusion in all groups except anephric subjects, and with angiotensin II administration in patients with mild to moderate renal failure or patients combined. These relationships were consistently closer than those between aldosterone responses and changes in PRA or basal PRA. However, postural aldosterone responsiveness at any given basal aldosterone level was significantly lower in patients with renal disease than in normal subjects, and this was associated with a parallel impairment in renin responsiveness. In contrast, when related to basal levels aldosterone responsiveness to ACTH or angiotensin II appreared to be comparable in normal subjects and patients with renal disease. Aldosterone responses to posture, ACTH, or angiotensin II did not correlate with associated changes in plasma cortisol, sodium, or potassium levels. These data suggest that basal adrenal secretory activity is a major factor conditioning aldosterone responsiveness to various stimuli in normal subjects as well as in patients with renal disease.

Studies of renin-aldosterone axis in stable normotensive and hypertensive renal allograft recipients

Functional aspects of the renin-aldosterone axis were investigated in long-term normotensive and hypertensive renal allograft recipients. Unstimulated plasma renin and aldosterone levels were within control range in all patients and rose significantly in response to sodium depletion. However, no difference in the stimulated renin and aldosterone values between normotensive and hypertensive patients was noted. Baseline aldosterone secretory rates were elevated in all patients, but were higher in hypertensive patients than in normotensive patients. In both groups sodium depletion failed to augment this already elevated aldosterone secretion rate. Possibly, changes in the body pool and/or metabolic clearance rate of aldosterone account for elevations in plasma levels despite a relatively fixed secretory rate, though the role played by the lack of normal innervation of the kidneys cannot be ignored. It is unknown whether these observations may be causal or affected by other presently unknown or unmonitored factors. This in part may reflect unfolding problems in the understanding of nonrenal transplant hypertension.

Aldosterone response to ACTH stimulation in anephric and non-nephrectomized patients on regular hemodialysis

The effect of ACTH on plasma aldosterone concentration (PAC) and plasma cortisol concentration (PCC) has been investigated in 5 anephric and 6 non-nephrectomized patients on regular homodialysis. Basal PAC was significantly lower (p less than 0.01) in the anephric (mean 37.6 pg/ml) than in the nonnephrectomized group (mean 117.5 pg/ml), whereas basal PCC (18.6 and 16.5 mug/100 ml, respectively) did not differ significantly (p less than 0.05). Following administration of synthetic beta1-24 ACTH, the maximal percentage increase in PAC was significantly lower ( less than 0.001) in the anephric (105%) than in the nonnephrectomized group (286%). The rise in PCC, 118%, in both groups showed no significant difference (p less than 0.05). The higher basal level of PAC and the more pronounced response to ACTH in nonnephrectomized patients correlated with higher basal levels of plasma renin activity compared with the anephric group. An influence of the remaining renin-angiotensin system on the ability to react to an ACTH stimulation is therefore suggested.

Hepatorenal syndrome: a disease mediated by the intrarenal action of renin

The functional renal failure accompanying advanced liver disease is characterized by azotemia, a urine of very low sodium concentration and systemic hypotension with decreased renal perfusion and high renal vascular resistance. Patients with this disorder have a markedly reduced ability to excrete free water and develop hyponatremia, ascites and edema. It is postulated that this renal dysfunction is due to hepatic failure to make renin substrate. Renin released from the kidney is thus unable to exert its pressor effect. The resultant hypotension and renal hypoperfusion continue to stimulate excessive synthesis and release of renin. It is postulated that the overdriven renal renin system increases renovascular resistance at the level of the glomerular arterioles. This causes decreased renal blood flow and decreased glomerular filtration rate leading to salt and water retention and azotemia. Since no renin substrate is available for human infusion, this hypothesis could be tested either by infusion of angiotensin II to restore systemic blood pressure and renal perfusion or by beta adrenergic blockade with propranolol to attempt to decrease the intrarenal effects of renin, restore glomerular blood flow and filtration and thus return of renal function.

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.

Anatomical and Physio-Pathological Basis of Neurohypophysial - Renal - Adrenal Feed-Back Systems Controlling Renal Function

It has been established that naturally occurring pressor agents (adrenaline vasopressin and angiotensin ii) are all potent renal vasoconstrictors and, of these, vasopressin is the longer lasting and provides a back-ground of renal vasotonicity without which the kidney is unable to concentrate. The vasoconstriction affects particularly the renal outer cortical vessels and vasa recta and is associated with temporary oliguria or anuria (antidiuresis of varying degree). In association with renal outer cortical vasoconstriction there is active dilatation of the vessels supplying the adrenal gland and ovary as revealed by arteriography. Since vasopressin exerts a variable degree of renal vasotonicity according to circumstances, there appears to be an integrated feed-back system linking the neurohypophys's and hormonal responses by the adrenal and ovary through which tubular function is controlled. Since the vascular conduits between the renal artery and the adrenal gland and ovary reveal individual variation, the feed-back system induces responses which vary from modest to hyper-reactive which goes some way to explain the nature of individual responses. Taken in conjunction with other data, the evidence, strongly indicates that hormonal responses by the adrenal gland and the ovary are associated with increased blood flow. The integrated feed-back system assures that increased blood flow to the adrenal gland accompanies the appropriate signal for hormonal release. The widespread involvement of vasopressin in the systems of the body and particularly its influence on tubular function, it has been concluded, derives mainly from its vasopressor effect.

The presented evidence suggests that the medullary arteries of Flint represent the original blood supply of the chromaffin mass which migrates within the adrenal cortex during foetal life. The medullary arteries and venae comites constitute an independent vascular system within the adrenal gland.