Efficacy and safety of the direct renin inhibitor aliskiren was compared with ramipril for treatment of essential systolic hypertension in elderly patients. A 36-week, randomized, double-blind, parallel-group, active-controlled, optional-titration study was performed in 901 patients (aliskiren, n ¼ 457; ramipril, n ¼ 444) X65 years of age with systolic blood pressure (SBP) X140 mm Hg. Aliskiren 150-300 mg per day or ramipril 5-10 mg per day for was administered for 12 weeks with optional add-on therapy of hydrochlorothiazide (12.5-25 mg per day) at week 12 and amlodipine (5-10 mg per day) at week 22. The primary end point was non-inferiority of aliskiren vs ramipril monotherapy for change from baseline in mean sitting SBP (msSBP) at week 12. Decreases from baseline msSBP and mean sitting diastolic BP with aliskiren monotherapy (À14.0 and À5.1 mm Hg, respectively) were non-inferior (Po0.001 for both values) and superior to ramipril monotherapy (À11.6, À3.6 mm Hg; P ¼ 0.02, Po0.01, respectively). More patients achieved BP control with aliskiren (42%) than ramipril (33%; Po0.01). At week 36, fewer patients receiving aliskiren-based therapy required add-on treatment with hydrochlorothiazide or amlodipine (P ¼ 0.01 and 0.048, respectively). Tolerability was similar, but more patients receiving ramipril reported cough (Po0.001). In elderly patients with systolic hypertension, aliskiren proved to be more effective and better overall anti-hypertensive therapy compared to ramipril.

A B S T R A C T Sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) is associated with electrolyte transport in many tissues. To help delineate its role in intestinal transport, changes in rat intestinal electrolyte and water transport induced by injecting methylprednisolone acetate 3 mg/100 g or deoxycorticosterone acetate (DOCA) 0.5 mg/100 g per day for 3 days were correlated with changes in Na-K-ATPase activity. Methylprednisolone increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the jejunum, ileum, and colon. Examination of isolated epithelial cells demonstrated that the jejunal and ileal increase in Na-K-ATPase occurred in both the villus tip and crypt areas. The time-courses of the ileal enzyme and transport changes were identical. Permeability, Mg-ATPase, and adenylate cyclase activities were unchanged by methylprednisolone. DOCA increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the colon alone. Colonic Mg-ATPase and adenylate cyclase activities were unaffected. Jejunal and ileal enzyme activity, electrolyte transport, and permeability were unchanged by DOCA. Methylprednisolone and DOCA were not additive in their effect on colonic Na-K-ATPase activity. Methylprednisolone and DOCA increased electrolyte and water transport and Na-K-ATPase activity concomitantly in specific segments of small intestine and colon. These data are consistent with an important role for Na-K-ATPase in intestinal electrolyte and water transport.

Short-chain fatty acid (SCFA) transport across the colon may occur by nonionic diffusion and/or via apical membrane SCFA−/[Formula: see text]exchange. To examine the relative importance of these processes, stripped segments of rat ( Ratus ratus) proximal and distal colon were studied in Ussing chambers, and the unidirectional fluxes of radiolabeled SCFA butyrate, propionate, or weakly metabolized isobutyrate were measured. In N-2-hydroxyethylpiperazine- N′-2-ethanesulfonic acid (HEPES) or 1 or 5 mM [Formula: see text] Ringer, decreases in mucosal pH stimulated mucosal-to-serosal flux ( J m→s) of all SCFA, decreases in serosal pH stimulated serosal-to-mucosal flux ( J s→m), and bilateral pH decreases stimulated both fluxes equally. These effects were observed whether the SCFA was present on one or both sides of the tissue, in both proximal and distal colon, in the absence of luminal Na+, and in the presence of either luminal or serosal ouabain. Changes in intracellular pH or intracellular [[Formula: see text]] did not account for the effects of extracellular pH. Luminal Cl− removal, to evaluate the role of apical membrane Cl−/SCFA−exchange, had no effect on J m→s but decreased J s→m 32% at pH 6.5 and 22% at 7.2. Increasing SCFA concentration from 1 to 100 mM, at pH 6.4 or 7.4, caused a linear increase in J m→s. We conclude that SCFA are mainly transported across the rat colon by nonionic diffusion.

Acute hypercapnia may develop during periodic breathing from an imbalance between abnormal ventilatory patterns during apnea and/or hypopnea and compensatory ventilatory response in the interevent periods. However, transition of this acute hypercapnia into chronic sustained hypercapnia during wakefulness remains unexplained. We hypothesized that respiratory-renal interactions would play a critical role in this transition. Because this transition cannot be readily addressed clinically, we modified a previously published model of whole-body CO2 kinetics by adding respiratory control and renal bicarbonate kinetics. We enforced a pattern of 8 h of periodic breathing (sleep) and 16 h of regular ventilation (wakefulness) repeated for 20 days. Interventions included varying the initial awake respiratory CO2 response and varying the rate of renal bicarbonate excretion within the physiological range. The results showed that acute hypercapnia during periodic breathing could transition into chronic sustained hypercapnia during wakefulness. Although acute hypercapnia could be attributed to periodic breathing alone, transition from acute to chronic hypercapnia required either slowing of renal bicarbonate kinetics, reduction of ventilatory CO2 responsiveness, or both. Thus the model showed that the interaction between the time constant for bicarbonate excretion and respiratory control results in both failure of bicarbonate concentration to fully normalize before the next period of sleep and persistence of hypercapnia through blunting of ventilatory drive. These respiratory-renal interactions create a cumulative effect over subsequent periods of sleep that eventually results in a self-perpetuating state of chronic hypercapnia.