Alberto B. Alonso

Effects of severe, uncontrolled hypertension on endothelial activation: soluble vascular cell adhesion molecule-1, soluble intercellular adhesion molecule-1 and von Willebrand factor.

Objectives The molecular mechanisms whereby severe, uncontrolled hypertension (SHT) is translated into acute vascular target organ dysfunction have not been completely defined. We sought to determine whether SHT is associated with pressure-dependent endothelial activation as assessed by soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1) and von Willebrand Factor (vWF). Methods We determined sVCAM-1, sICAM-1 and vWF in three groups: (i) untreated patients referred specifically for treatment of SHT [diastolic blood pressure (DBP) ⩾ 120 mmHg;n = 24]; (ii) untreated patients with established mild hypertension (MHT; DBP 95–100 mmHg;n = 19); and (iii) normotensive volunteers (DBP ⩽ 90;n = 16). Results By analysis of variance, sVCAM-1 (P = 0.002), sICAM-1 (P = 0.02) and vWF (P = 0.009) were greater in SHT and MHT than in normotensives but did not differ between SHT and MHT. We observed a significant positive correlation between blood pressure and soluble activation markers at lower blood pressures (normotensives and MHT considered together) that was not present in SHT. Conclusions Even mild elevation of blood pressure may be sufficient to activate the expression of adhesion molecules. Mechanisms other than the endothelial expression of adhesion molecules may be important in mediating the accelerated target organ injury produced by SHT in humans. Concentrations of soluble adhesion molecules and vWF may depend more strongly upon factors in the hypertensive microenvironment other than the absolute level of blood pressure.

Additive effect of drospirenone/17-β-estradiol in hypertensive postmenopausal women receiving enalapril ☆

BACKGROUND Aldosterone has been implicated in the pathogenesis of progressive cardiovascular disease. Drospirenone (DRSP) is a novel progestin with aldosterone receptor antagonist activity developed for hormone replacement therapy (HRT) as DRSP/17beta-estradiol (DRSP/ E2). We investigated the additive effect of DRSP/E2 versus placebo on 24-h ambulatory blood pressure (BP) in postmenopausal women with hypertension treated with enalapril maleate (ENA). METHODS This was a double-blind, randomized, two-parallel group trial. Twenty-four nonsmoking postmenopausal women receiving 10 mg of ENA twice a day before study were randomized to DRSP/E2 + ENA (n = 12) or placebo (P) + ENA (n = 12) for 14 days. Twenty-four-hour ambulatory BP, plasma renin activity, and serum aldosterone were determined at baseline and on day 14. RESULTS Compared to placebo, 24-h mean [SD] BP in the DRSP/E2 + ENA group decreased significantly from baseline (139/80 mm Hg), systolic (-9 [51 mm Hg, P = .014) and diastolic (-5 [4] mm Hg, P = .007). Essentially no change from baseline (139/83 mm Hg) in systolic or diastolic 24-h ambulatory BP were observed in the P + ENA group. Aldosterone (mean [SD]) increased from baseline by 2.6 [4.5] ng/dL in the DRSP/E2 + ENA group, and decreased by 0.3 [5.5] ng/dL in the P + ENA group (P = .08) consistent with an antimineralocorticoid effect. CONCLUSIONS Our results suggest a significant additive BP-lowering effect of DRSP/E2 on both systolic and diastolic BP in hypertensive postmenopausal women receiving ENA, consistent with an antimineralocorticoid effect. DRSP/E2, a HRT with antimineralocorticoid effects, could offer a novel potential mechanism for reducing cardiovascular end points in postmenopausal women.

Mechanisms of Impaired Potassium Handling With Dual Renin-Angiotensin-Aldosterone Blockade in Chronic Kidney Disease

The combination of an aldosterone receptor antagonist added to an angiotensin-converting enzyme inhibitor has been demonstrated to reduce cardiovascular and renal end points in hypertensive humans but can produce hyperkalemia in the common clinical setting of impaired renal function. We investigated the effects of dual therapy on acute and chronic potassium handling in hypertensive humans with renal impairment by conducting a randomized crossover clinical trial of 4 weeks of 40 mg lisinopril/25 mg spironolactone versus placebo in 18 participants with a glomerular filtration rate of 25 to 65 mL/min. Study end points, following an established protocol, were hourly determinations of dynamic renal potassium excretion (mmol/h) and serum potassium (mmol/L) after 35 mmol oral potassium challenge in addition to ambulatory potassium concentration. After 4 weeks, ambulatory potassium concentration was 4.87 mmol/L with lisinopril/spironolactone versus 4.37 with placebo (P<0.001). Lisinopril/spironolactone produced only a modest 0.44 mmol/h reduction in stimulated potassium excretion (P=0.03) but a substantial 0.67 mmol/L increase in serum potassium (P<0.001) in response to 35 mmol potassium; these findings are consistent with impaired extrarenal/transcellular potassium disposition. We found the increase in serum potassium after an oral potassium challenge to be a strong predictor of the increase in ambulatory potassium with lisinopril/spironolactone. Our study suggests that dual renin-angiotensin-aldosterone blockade may impair extrarenal/transcellular potassium disposition in addition to reducing potassium excretion in humans with renal impairment, and that acute changes in dynamic potassium handling are predictive of chronic changes in ambulatory potassium concentration with dual renin-angiotensin-aldosterone blockade.

Randomized, placebo-controlled trial of the effects of drospirenone-estradiol on blood pressure and potassium balance in hypertensive postmenopausal women receiving hydrochlorothiazide

Objective:Drospirenone (DRSP), a spironolactone analog with aldosterone antagonist activity, is a novel progestogen developed for use as hormone therapy in postmenopausal women in combination with 17&bgr;-estradiol (E2). DRSP/E2 lowers blood pressure when used alone in hypertensive postmenopausal women or when administered concomitantly with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. DRSP/E2 has not been studied in combination with the widely prescribed hydrochlorothiazide (HCTZ). We investigated the effects of 3 mg DRSP/1 mg E2 versus placebo on blood pressure and potassium balance when added to existing therapy with 25 mg HCTZ in postmenopausal women with established stage I hypertension. Design:This was a single-center, double-blind, randomized, placebo-controlled, two-treatment, two 4-week treatment period crossover study in 36 postmenopausal women with stage I hypertension maintained on 25 mg HCTZ. The endpoint was a change from baseline in systolic and diastolic blood pressures by 24-hour ambulatory blood pressure monitoring. Safety monitoring included serum potassium (mEq/L) and adverse events. Results:Mean systolic and diastolic blood pressures by 24-hour ambulatory blood pressure monitoring were reduced significantly, by −7.2 and −4.5 mm Hg, respectively, with DRSP/E2 as compared with placebo. The decrease in potassium with HCTZ was 0.2 mEq/L less with DRSP/E2 than placebo, suggesting a potassium-sparing effect. The most frequently observed adverse events with DRSP/E2 were vaginal bleeding and breast tenderness, which were attributable to the hormone therapy. Conclusions:DRSP/E2 substantially lowers systolic and diastolic blood pressure when added to existing antihypertensive therapy with HCTZ in hypertensive postmenopausal women. In addition, DRSP/E2 has a potassium-sparing effect that counteracts HCTZ-induced potassium loss.

Comparative Effects on Dynamic Renal Potassium Excretion of ACE Inhibition versus Angiotensin Receptor Blockade in Hypertensive Patients with Type II Diabetes Mellitus

Both ACE inhibitors (ACEI) and angiotensin receptor blockers (ARB) are renoprotective beyond their effects on blood pressure (BP), but their widespread use is limited by theirtendency to provoke hyperkalemia. The comparative effects of ACEI and ARB on potassium handling have not been investigated. The objective of this study was to determine whether there are differences in dynamic renal potassium handling between ACEI and ARB in response to an oral potassium challenge. This was a randomized crossover study of candesartan versus lisinopril titrated to control BP followed by an inpatient study of renal potassium handling in 24 hypertensive patients with type II diabetes mellitus (DMII) and preserved renal function. Following an oral potassium challenge (0.75 mmol/kg), differences in hourly serum K (mmol/L), rate of urinary potassium excretion (UkV, micromol/min), and fractional excretion of potassium (FEK) were assessed by repeated‐measures ANOVA. Hourly UkV (p = .45) and FEK (p = .19) were similar for candesartan and lisinopril, although FEK at 2 hours for candesartan tended to exceed that for lisinopril (.34 [.04] vs. .26 [.03]) and approached significance (p = .096). UkV for candesartan at hour 2 was 177 (26) and 121 (21) for lisinopril and also approached significance (p = .10). Serial serum potassium did not differ (p = .70). No statistical differences were discovered in renal potassium handling between candesartan and lisinopril in patients with DM II and preserved renal function. Whether there are differences between the drug classes in renal impairment remains to be determined.

Evidence for a gastrointestinal–renal kaliuretic signaling axis in humans

A gastrointestinal-renal kaliuretic signaling axis has been proposed to regulate potassium excretion in response to acute potassium ingestion independent of the extracellular potassium concentration and aldosterone. Here we studied this presumed axis in 32 individuals in our clinical pharmacology unit while on a 20 mmol sodium and 60 mmol potassium diet. The serum potassium concentration, potassium excretion, aldosterone, and insulin were measured following either a 35 mmol oral potassium load, a potassium- and sodium-deficient complex meal, or a potassium-deficient complex meal plus 35 mmol potassium. This design allowed determination of the component effects on potassium handling of the meal and potassium load separately. The meal plus potassium test was repeated following aldosterone blockade with eplerenone to specifically evaluate the role of aldosterone. In response to the potassium-deficient meal plus 35 mmol potassium, the serum potassium did not increase but the hourly mean potassium excretion increased sharply. This kaliuresis persisted following aldosterone blockade with eplerenone, further suggesting independence from aldosterone. Thus, a gastrointestinal-renal kaliuretic signaling axis exists in humans mediating potassium excretion independent of changes in the serum potassium concentration and aldosterone. The implication of this mechanism is yet to be determined but may account for a significant component of potassium excretion following a complex potassium-rich meal.

Sodium challenge does not support an acute gastrointestinal–renal natriuretic signaling axis in humans

A gastrointestinal-renal natriuretic signaling axis has been proposed to regulate sodium excretion in response to acute sodium ingestion. Such an axis is thought to be regulated by a gastrointestinal sodium sensor coupled to the activation/release of a natriuretic signal and could have important clinical and scientific implications. Here we systematically tested for this putative axis and the potential involvement of the gastrointestinal-derived natriuretic prohormones prouroguanylin and proguanylin in 15 healthy volunteers. There was no difference in sodium excretion following equivalent oral or intravenous sodium loads during either high- or low-sodium diets. Furthermore, serum concentrations of prouroguanylin and proguanylin did not increase, did not differ following oral or intravenous sodium, and did not correlate with sodium excretion. Thus, our results do not support an acute gastrointestinal-renal natriuretic axis or a central role for prouroguanylin or proguanylin in humans. If such an axis does exist, it is not characterized by a significant difference in the pattern of sodium excretion following either an oral or intravenous sodium load.

Comparative Pharmacokinetics and Pharmacodynamics of Amlodipine in Hypertensive Patients with and without Type II Diabetes Mellitus

Recent clinical trials aimed at attenuating complications in diabetes mellitus have generated interest in the impact of drug formulation and altered pharmacokinetics and pharmacodynamics in diabetes. Specifically, it has been proposed that the diabetic state may alter the pharmacokinetics of several cardiovascular drugs, including some calcium antagonists. The present study investigates the effects of diabetes mellitus on the pharmacokinetics and pharmacodynamics of amlodipine in hypertensive subjects with and without diabetes mellitus to determine whether the diabetic state alters these parameters. This trial consisted of a 2‐week placebo washout phase, a 2‐week titration phase, and a 2‐week maintenance phase. Study patients included 18 hypertensive patients with type II diabetes mellitus and 10 nondiabetic hypertensive patients. Blood samples were collected after administration of amlodipine and AUC, Cmax, and tmax were determined. The acute 24‐hour pharmacodynamic response to amlodipine was assessed by blood pressure and telemetric heart rate measurements. There were no significant differences for either amlodipine 5 or 10 mg in AUC (p = 0.40 for 5 mg; p = 0.59 for 10 mg), Cmax (p = 0.41 for 5 mg; p = 0.45 for 10 mg), and tmax (p = 0.79 for 5 mg; p = 0.67 for 10 mg) between diabetic and nondiabetic hypertensive subjects. Similarly, the 24‐hour pharmacodynamic effects of amlodipine on systolic blood pressure, diastolic blood pressure, and heart rate did not differ between diabetic and nondiabetic subjects as assessed by repeated‐measures analysis of variance. Because of the theoretical basis for anticipating that diabetes mellitus may provoke important pharmacokinetic and pharmacodynamic alterations, our study provides an important database in clearly demonstrating that the diabetic milieu did not alter the pharmacokinetics or pharmacodynamics of amlodipine.

Effects of selective vs. nonselective cyclooxygenase inhibition on dynamic renal potassium excretion: a randomized trial.

Both selective and nonselective cyclooxygenase (COX) inhibitors can reduce potassium excretion and can produce or exacerbate hyperkalemia. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 We investigated whether there is a difference between the effects of nonselective COX‐1/COX‐2 inhibitors and selective COX‐2 inhibitors on provoked dynamic renal potassium excretion. We apply a mixed‐effects model statistical approach that allows investigation of drug‐induced delays in reaching maximal potassium excretion, blunting/flattening of potassium handling curves, and shift/separation in potassium handling at peak potassium excretion.

Pharmacokinetics and pharmacodynamics of drospirenone-estradiol combination hormone therapy product coadministered with hydrochlorothiazide in hypertensive postmenopausal women.

The effects of combination hormone therapy of drospirenone (DRSP), a novel progestin with antialdosterone properties, and 17β‐estradiol (E2) on hydrochlorothiazide (HCTZ) pharmacokinetics/pharmacodynamics versus placebo were investigated in a double‐blind, placebo‐controlled, crossover study. Thirty‐six postmenopausal women with stage 1 hypertension maintained on 25 mg of HCTZ once daily were randomized to receive either 3 mg of DRSP/1 mg of E2 or placebo once daily for 4 weeks. Plasma HCTZ, serum DRSP, E2, potassium, aldosterone, and plasma renin activity were determined at baseline and after 4 weeks. Results showed that the combination of DRSP/E2 plus 25 mg of HCTZ is safe and well tolerated in hypertensive postmenopausal women. The pharmacokinetics of HCTZ were not affected by coadministration of DRSP/E2. The geometric mean ratios and 90% confidence intervals ([HCTZ + DRSP/E2]/[HCTZ + placebo]) for HCTZ (a) area under the serum/plasma concentration‐time curve from 0 to 24 hours and (b) maximum plasma concentration were 101 (90.7, 112) and 103 (92.8, 115), respectively. In the HCTZ + DRSP/E2 group, serum potassium, aldosterone, and plasma renin activity all increased in a manner marginally consistent with a beneficial antialdosterone effect, counteracting the HCTZ‐induced potassium loss and lowering both systolic and diastolic blood pressure. No dose adjustment is required when DRSP/E2 is added to antihypertensive therapy with HCTZ in hypertensive postmenopausal women.