Plasma renin activity and aldosterone in dogs with portosystemic collaterals

We investigated the possibility that angiotensin II (ANGII) augments the sensitivity of the pituitary to corticotropin releasing factor (CRF) by comparing, in patients with essential hypertension, the responses of plasma adrenocorticotropic hormone (ACTH), cortisol, aldosterone, and renin activity to a bolus injection of either 0.5 or 1.0 microgram/kg of synthetic ovine CRF in control conditions and after chronic treatment with the converting enzyme inhibitor captopril to block the formation of ANGII; the effects of CRF were examined up to 4 h after its administration. In control studies, we found that the two doses of CRF induced similar increments in ACTH and cortisol, the levels of which remained elevated throughout the studies; these changes were associated with increments in plasma aldosterone that were dose dependent, less pronounced, and of shorter duration and with a slight decrease in plasma renin activity. Captopril treatment increased basal plasma renin activity and lowered plasma aldosterone while leaving basal ACTH and cortisol unchanged. During converting enzyme inhibition, the responses of ACTH and cortisol to CRF were similar to those observed in control studies, whereas the changes in plasma aldosterone and plasma renin activity were, respectively, smaller and greater. From these results, it appears that during ANGII blockade the sensitivity of ACTH to CRF stimulation is unaffected, whereas that of the adrenals to ACTH is selectively reduced at the level of the zona glomerulosa.

The renin–aldosterone axis in kidney transplant recipients and its association with allograft function and structure

Elderly patients with hyperkalaemia often have low concentrations of plasma renin and aldosterone, perhaps secondary to reduced glomerular filtration and sympathetic insufficiency. The endocrine response to surgical stress and volume expansion during anaesthesia was studied in seven elderly patients with hyperkalaemia (mean age 87.7 +/- SD 5.3 years), 18 elderly patients without hyperkalaemia (86.5 +/- 5.5 years), and 18 younger patients (52.6 +/- 7.2 years) as controls. Base-line values, in hyperkalaemic elderly patients, for plasma renin activity and plasma aldosterone concentration were 0.8 +/- 0.3 ng mL-1 h-1 and 2.8 +/- 0.8 pg mL-1 respectively (significantly lower than in the younger patients), and 287 +/- 42 pg mL-1 for plasma atrial natriuretic peptide levels, which were significantly higher. The plasma renin activity and aldosterone concentrations in elderly patients with hyperkalaemia were at all times lower, but not significantly, than those of the elderly patients without hyperkalaemia. The atrial natriuretic peptide concentrations (351 +/- 48 pg mL-1) in the hyperkalaemic elderly were significantly higher 90 min after induction of anaesthesia than in the normokalaemic elderly (108 +/- 38 pg mL-1). Hormone concentrations in the hyperkalaemic patients did not change during anaesthesia, but plasma atrial natriuretic peptide concentrations increased significantly in the normokalaemic elderly, and plasma renin activity and aldosterone of the younger patients increased significantly during anaesthesia. These results indicate that plasma renin activity, and the concentrations of aldosterone and of atrial natriuretic peptide in elderly patients with hyperkalaemia are unresponsive to surgical stress and volume expansion.

We hypothesized that the aldosterone: renin ratio (ARR) predicts the antihypertensive response to mineralocorticoid receptor antagonist, spironolactone (SPIRO), when compared with bendroflumethiazide (BFZ). We conducted a randomized, crossover, trial on hypertensive patients with either high ARR (HARR defined as >750 and plasma aldosterone >250 pmol/l) or low ARR (LARR defined as <300 and plasma renin activity <10 ng/ml per h). Each group took SPIRO 50 mg once daily for 12 weeks and BFZ 2.5 mg once daily for 12 weeks in random order separated by 2-week washout. Patients with mean 24-h systolic ambulatory blood pressure (SABP) at least 140 mmHg were included. Primary endpoint was difference in SABP between SPIRO and BFZ in patients with HARR compared with those with LARR. One hundred and eleven patients (60 HARR and 51 LARR) completed the study. SABP at 12 weeks in the HARR group was 129.4 mmHg on SPIRO and 134.4 mmHg on BFZ [difference -5.01; 95% confidence interval (CI) -7.51, -2.52; P < 0.0002]. In the LARR group, SABP was 129.7 mmHg on SPIRO and 133.1 mmHg on BFZ [difference -3.43 (95% CI -6.18, -0.68) P < 0.01]. Difference between groups (HARR vs. LARR) was -1.58 mmHg (95% CI 5.25, -2.08; not significant, P = 0.394). In a secondary analysis of the overall study population of 111 patients, SABP reduction with SPIRO 50 mg was superior to BFZ 2.5 mg [SPIRO -14.8 mmHg, BFZ -10.5 mmHg, difference -4.29 mmHg (95% CI -6.12, -2.46)]. Results were similar for secondary endpoints. Plasma renin activity or aldosterone did not predict blood pressure response to SPIRO. Results were independent of concomitant angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use. The ARR did not predict the blood pressure response to SPIRO. SPIRO 50 mg was significantly more effective than BFZ 2.5 mg in lowering SABP irrespective of baseline ARR, plasma renin activity or aldosterone.

Renin-aldosterone system and atrial natriuretic peptide during anesthesia in orthopedic patients over 80 years of age

It is well known the primary aldosteronism (PA) is most common endocrinological hypertension and accounted for 10% among all hypertension population, and it develops cardiovascular disease more frequently than blood pressure matched essential hypertension. Those patients with bilateral hyperaldosteronism, called idiopathic hyperaldosteronism (IHA), or unwilling for surgical treatment are treated by mineralcorticoid receptor antagonists (MRAs). Although it had been unclear how titrate MRAs to prevent atherosclerotic cardiovascular events, a managemental target for those patients was recently reported as plasma renin activity (PRA) ≥ 1.0 ng/ml/hr to prevent cardiovascular events (Hundemer GL, et. al. Lancet Diabetes Endocrinol. 2018 Jan;6(1):51-59).Thus, we investigated 77 cases of adrenal venous sampling performed patients with PA and followed up for 3 years in our hospital since 2007, including 24 males and 53 females, and their mean age was 56.3 ± 12.5 years old. All patients underwent AVS and showed bilateral hyperaldosteronism and treated with MRAs and followed up more than 3 years. We collected blood pressure, serum sodium and potassium concentration, estimated glomerular filtration ratio (eGFR), PRA, plasma aldosterone concentration (PAC), atherosclerotic parameter, such as mean intima media thickness (IMT), brachial-ankle pulse wave velocity (baPWV) and ankle-brachial index (ABI). We evaluated the relationship of those patients’ PRA and aldosterone to renin ratio (ARR) with eGFR, IMT, baPWV, and ABI. The change of mean IMT after 3 year-follow up were 0.03 ± 0.11 mm vs. 0.06 ± 0.09 mm for well controlled (PRA ≥ 1.0 ng/ml/hr) and poorly controlled (PRA < 1.0 ng/ml/hr), respectively, and no significant difference between them. In the other hand, the change of mean IMT after 3 year-follow up showed 0.03 ± 0.10 mm vs. 0.08 ± 0.10 mm for well controlled (PRA ≥ 1.0 ng/ml/hr and ARR <20) and poorly controlled (PRA < 1.0 ng/ml/hr or ARR ≥ 20), respectively, and the mean IMT increase was significantly lower in this group.The mean IMT increase showed significantly lower only with PRA ≥ 1.0 ng/ml/hr and ARR <20 rather than PRA ≥ 1.0 ng/ml/hr alone.In our results, both PRA ≥ 1.0 ng/ml/hr and ARR<20 are important to prevent or improve atherosclerosis, rather than only PRA ≥ 1.0 ng/ml/hr and should be titrated MRAs to achieve this target.In conclusion, our result revealed the titration of MRAs is important to prevent atherosclerotic cardiovascular event and not only PRA ≥ 1.0 ng/ml/hr, but both PRA and ARR <20 should be achieved.

Background Primary aldosteronism (PA) is a common cause of hypertension, whereby uncontrollable amounts of aldosterone are produced by a benign tumour or hyperplasia of the adrenal glands. Excess aldosterone results in significant sodium reabsorption in the kidneys, increasing water retention and blood volume, thereby causing hypertension. The renin-angiotensin-aldosterone system (RAAS) regulates the production of aldosterone and in this system, renin and aldosterone should move in synchronicity with each other throughout the day. Therefore, these two components are used to assess the status of the RAAS, particularly in the evaluation of new therapies in clinical research studies. Historically, the assessments of aldosterone and plasma renin activity (PRA) have been performed using separate methods using immunoassay or more recently liquid chromatography - tandem mass spectrometry (LC-MS/MS) platforms. One of the benefits of using LC-MS/MS for clinical research is the ability to measure multiple analytes across the proteome and metabolome using the same system and even in the same analysis to provide more information in less time and save costs. Here we evaluate a single LC-MS/MS method for the combined measurement of plasma aldosterone and renin activity for clinical research purposes. Methods Aldosterone certified reference material (Merck, UK) and Angiotensin I (Cambridge BioScience, UK) were used to create calibrators in 2% Bovine Serum Albumin (BSA) in Phosphate Buffered Saline (PBS). In-house QC material prepared in both 2% BSA in PBS and K2EDTA plasma (BioIVT, UK), were used to evaluate method precision. Plasma samples were analyzed using the newly developed method and the quantified results were compared to separate independent LC-MS/MS methods for aldosterone and plasma renin activity. Plasma samples were treated with generation buffer (Sodium acetate, EDTA, acetic acid, SBTI and PMSF) and mixed for three hours at 37 °C. Samples were precipitated, diluted and centrifuged prior to SPE. Sample supernatant was transferred to a Waters Oasis™ µElution 96 Well Plate, followed by a wash and elution. Using an ACQUITY™ UPLC™ I-Class System, samples were injected onto a Waters XBridge™ C8, 2.5 µm, 2.1 × 50 mm Column using a water/methanol/ammonium fluoride gradient elution profile and quantified with a Waters Xevo™ TQ Absolute Mass Spectrometer. Results The method demonstrated no significant carryover or matrix effects and was shown to be linear from 10 - 2500 pg/mL for aldosterone and 0.1–25 ng/mL/h for PRA. Analytical sensitivity investigations indicate the analytical sensitivity of this method would allow precise quantification (&amp;lt;20%) at 10 pg/mL and 0.1 ng/mL/h, for aldosterone and PRA, respectively. Coefficients of variation (CV) for total precision and repeatability on 5 analytical runs for low, mid and high QCs were all &amp;lt;10% (n = 25) for aldosterone and PRA. Comparison with samples previously analyzed by an independent LC-MS/MS method demonstrated good agreement for aldosterone and PRA. Conclusions We have successfully quantified aldosterone and renin activity in plasma in a single method using an SPE protocol with LC-MS/MS analysis, for clinical research purposes. The method demonstrates excellent linearity and precision, with minimal matrix effects. For Research Use Only. Not for Use in Diagnostic Procedures.

The effect of 90-min heat exposure (46 degrees C, 35 mbar) on plasma aldosterone (PA) patterns was studied and the respective roles of plasma renin activity (PRA), adrenocorticotropin (ACTH), Na+ and K+ concentrations in the control of PA response were in investigated in eight subjects on a low sodium diet and in five subjects on a high sodium diet. In all subjects, transitory PA increases of varying importance were observed, which were not related to sweat losses (less than 1% bodyweight) or to rectal temperature rise. In sodium-repleted subjects, basal PA and PRA levels as well as heat-induced rises were low (mean PA peak level = 12.62 +/- 1.15 ng/100 ml). They were enhanced by sodium depletion and PA reached a mean peak level of 34.07 +/- 2.73 ng/100 ml. But, in both conditions, the heat-induced PA peaks were 3-times higher than the initial levels. PA correlated with PRA in all but one of the sodium-repleted subjects and in 6 of the 8 sodium-depleted subjects. ACTH release, as measured by plasma cortisol (PC) levels, occurred in those subjects who noted an increased feeling of annoyance and discomfort. Thus, PA correlated positively with PC in 4 sodium-depleted subjects. A high sodium intake improved heat-tolerance. Plasma K+ and Na+ concentrations were not significantly modified by exposure to heat. PA increases can occur without concomitant changes in PRA, PC, K+ or Na+, which suggests that an additional factor may play a role in aldosterone regulation during acute heat exposure.

Analysis of postoperative biochemical values and clinical outcomes after adrenalectomy for primary aldosteronism

Ten patients with benign essential hypertension were studied after sodium loads and during sodium depletion induced by diet and diuretic. Sodium intake of 400 mEq/day did not produce the expected fall in aldosterone secretion or supine plasma aldosterone concentration, which remained within or above the limits observed in normal men on an intake of 120 mEq of sodium. One patient with suppressed plasma renin activity (PRA), high urinary and plasma aldosterone and normal cortisol, had bilaterally enlarged adrenals containing small cortical nodules. Five other patients had low PRA, which did not rise normally on standing or during sodium deprivation, but could be stimulated by further diuretic-induced sodium loss. Two of these 5 cases, studied on a high sodium intake, had trivial increases in plasma aldosterone after standing, but the others had large postural increases without significant change in PRA, plasma cortisol, or plasma sodium or potassium concentration. PRA, aldosterone secretion rate and plasma aldosterone concentration increased during sodium depletion. A large rise in plasma aldosterone was observed in the sodium-depleted hypertensive patients after 4 hr of standing and quiet ambulation. The increases in aldosterone secretion rate and plasma aldosterone concentration following sodium deprivation and standing were generally well correlated with increased PRA. The plasma aldosterone concentrations found in sodium-loaded hypertensives are not readily explained on the basis of regulation by the renin-angiotensin system, and deserve further critical study.

The day to day variations in plasma aldosterone and plasma renin activity throughout the menstrual cycle have been investigated in healthy young women. A sensitive and specific radioimmunoassay for the measurement of plasma aldosterone is described. The actual hormone parameters have been correlated with fluctuations in plasma oestradiol and progesterone, and LH has been measured for the determination of time of ovulation. Plasma renin activity and plasma aldosterone gradually increased two to four times from the early follicular to the mid-luteal phase, in accordance with earlier observations. In one woman using a beta adrenergic blocking agent plasma renin activity rose only slightly, whereas a normal rise in plasma aldosterone was noted. Another woman became pregnant during the cycle investigated. In this subject neither plasma renin activity nor plasma aldosterone decreased at the end of the cycle. Plasma aldosterone was almost doubled on the pre-ovulatory day, as compared with the early follicular phase, whereas no significant change in plasma renin activity or plasma renin substrate was found. The cause of this pre-ovulatory increase in plasma aldosterone is not known.

A pathogenetic role of the renin-angiotensin-aldosterone system has been implicated in cats in both systemic arterial hypertension and hypokalemic myopathy. Yet, measurement of plasma aldosterone concentrations (PACs) and plasma renin activity (PRA) has not unequivocally pointed to hyperaldosteronism as a cause of these conditions. To obtain appropriate reference ranges, this study included a large number (130) of healthy house cats of different breeds without a history of recent illness and plasma concentrations of urea and creatinine below the upper limit of the respective reference ranges. In addition, the pituitary-adrenocortical axis was studied by measuring plasma concentrations of adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), and cortisol. Reference ranges for PACs (110-540 pmol/L; 40-195 pg/mL), PRA (60-630 fmol/L/s; 0.3-3 ng/mL/h), and the aldosterone to renin ratio (ARR) (0.3-3.8) were very similar to those established in the same laboratory for humans in a supine position. No breed differences were found. The ARRs in neutered cats were significantly higher than in intact cats, primarily because of low PRA in neutered cats. The ARRs of cats > or = 5 years of age were significantly higher than those of cats < 5 years of age. The plasma concentrations of ACTH, alpha-MSH, and cortisol did not correlate significantly with PAC. Thus, although blood sampling was performed in cats in nonstandardized positions and was associated with a wide variation of stress responses, the references ranges of PAC, PRA, and ARR were similar to the relatively narrow limits established for humans under standardized conditions. The effects of neutering and aging on PRA and ARR warrant further investigation.

To assess the effect of obstructive sleep apnea treatment on plasma renin activity (PRA) and plasma aldosterone seven male patients were studied under two conditions: untreated and treated with nasal continuous positive airways pressure (CPAP). PRA and plasma aldosterone were measured at 10-min intervals for both nights. CPAP treatment diminished the urinary and Na+ excretion, whereas plasma volume increased. The mean levels of PRA and aldosterone were significantly enhanced by the treatment, increasing respectively from 1.5 +/- 0.3 to 3.0 +/- 0.7 ngAI ml-1.hr-1 (p less than 0.05) and from 8.0 +/- 1.0 to 12.0 +/- 1.7 ng.100 ml-1 (p less than 0.05). PRA curves reflected the overall sleep structure as similarly described in normal subjects. The apnea-induced sleep disturbance led to flat PRA profiles and the restoration of a normal sleep pattern by treatment restored the PRA oscillations related to the sleep cycles and consequently restored aldosterone oscillations. The mean amplitude of these oscillations increased respectively from 1.0 +/- 0.1 to 1.8 +/- 0.4 ngAI ml-1.hr-1 and from 5.4 +/- 1.2 to 10.9 +/- 1.9 ng.100 ml-1. These results suggest that CPAP treatment modifies the nocturnal patterns of PRA and aldosterone by increasing their mean levels and their oscillation amplitude. This indicates increased secretion, which contributes to the normalization of urine and Na output.

Eight infants had paired measurements of plasma aldosterone and plasma renin activity while being treated for congestive heart failure. There is parallelism with aldosterone and renin activity in the presence of a hyperactive renin-angiotensin-aldosterone system. Six patients had plasma renin activity and plasma aldosterone measured after commencing captopril and we have shown biochemical blockade of the renin-angiotensin-aldosterone system.

The Aldosterone-Renin Ratio and Primary Aldosteronism