Key pointsr 'Classic' cardiotonic steroids (CTSs) all inhibit Na + ,K + -ATPase (Na + pumps) and exert cardiotonic and vasotonic effects. Nevertheless, prolonged ouabain, but not digoxin, administration induces hypertension; moreover, digoxin antagonizes the hypertensinogenic effect of ouabain.r To examine acute ouabain-digoxin interactions, we tested these and related CTSs on myogenic tone (MT) in pressurized rat mesenteric small arteries and glutamate-evoked Ca 2+ transients in primary cultured rat hippocampal neurones.r The CTSs (0.3-10 nM) all augmented MT at 70 mmHg and Ca 2+ signals, but separated into two functional groups according to whether they were ouabain-or digoxin-like. CTSs within each group were synergistic, but between groups, were antagonistic to one another in both assays.r Na + pump αβ protomers may function as tetraprotomers ((αβ) 4 ) with quarter-site reactivity; simultaneous ouabain-and digoxin-like molecule binding promotes tetraprotomer disaggregation, enabling partial protomer reactivation.r These results may reveal why some patients respond poorly to digoxin therapy, and why Na + pumps may be a novel target for therapeutic development.Abstract 'Classic' cardiotonic steroids (CTSs) such as digoxin and ouabain selectively inhibit Na + ,K + -ATPase (the Na + pump) and, via Na + /Ca 2+ exchange (NCX), exert cardiotonic and vasotonic effects. CTS action is more complex than previously thought: prolonged subcutaneous administration of ouabain, but not digoxin, induces hypertension, and digoxin antagonizes ouabain's hypertensinogenic effect. We studied the acute interactions between CTSs in two indirect assays of Na + pump function: myogenic tone (MT) in isolated, pressurized rat mesenteric small arteries, and Ca 2+ signalling in primary cultured rat hippocampal neurones. The 'classic' CTSs (0.3-10 nM) behaved as 'agonists': all increased MT 70 (MT at 70 mmHg) and augmented glutamate-evoked Ca 2+ (Fura-2) signals. We then tested one CTS in the presence of another. Most CTSs could be divided into ouabain-like (ouabagenin, dihydroouabain (DHO), strophanthidin) or digoxin-like CTS (digoxigenin, digitoxin, bufalin). Within each group, the CTSs were synergistic, but ouabain-like and digoxin-like CTSs antagonized one another in both assays: For example, the ouabain-evoked (3 nM) increases in MT 70 and neuronal Ca 2+ signals were both greatly attenuated by the addition of 10 nM digoxin or 10 nM bufalin, and vice versa. Rostafuroxin (PST2238), a digoxigenin derivative that displaces 3 H-ouabain from Na + ,K + -ATPase, and attenuates some forms of hypertension, antagonized the effects of ouabain, but not digoxin. SEA0400, a Na + /Ca 2+ exchanger (NCX) blocker, antagonized the effects of both ouabain and digoxin. CTSs bind to the α subunit of pump αβ protomers. Analysis of potential models suggests that, in vivo, Na + pumps function as tetraprotomers ( (αβ) of a single CTS to one protomer blocks all pumping activity. The paradoxical ability of digoxin-like CTSs to reactivate the ouabain-inhibited com...

Low-dose ouabain constricts small arteries from ouabain-hypertensive rats: implications for sustained elevation of vascular resistance. Am J Physiol Heart Circ Physiol 297: H1140 -H1150, 2009. First published July 17, 2009 doi:10.1152/ajpheart.00436.2009.-Prolonged ouabain administration to normal rats causes sustained blood pressure (BP) elevation. This ouabain-induced hypertension (OH) has been attributed, in part, to the narrowing of third-order resistance arteries (ϳ320 m internal diameter) as a result of collagen deposition in the artery media (see Ref. 6). Here we describe the structural and functional properties of fourth-order mesenteric small arteries from control and OH rats, including the effect of low-dose ouabain on myogenic tone in these arteries. Systolic BP in OH rats was 138 Ϯ 3 versus 124 Ϯ 4 mmHg in controls (P Ͻ 0.01). Pressurized (70 mmHg) control and OH arteries, with only a single layer of myocytes, both had ϳ165-m internal diameters and ϳ20-m wall thicknesses. Even after fixation, despite vasoconstriction, the diameters and wall thicknesses did not differ between control and OH fourth-order arteries, whereas in third-order arteries, both parameters were significantly smaller in OH than in controls. Myogenic reactivity was significantly augmented in OH fourth-order arteries. Nevertheless, phenylephrine-(1 M) and high K ϩ -induced vasoconstrictions and acetylcholine-induced vasodilation were comparable in control and OH arteries. Vasoconstrictions induced by 5 M phenylephrine and by 10 mM caffeine in Ca 2ϩ -free media indicated that releasable sarcoplasmic reticulum Ca 2ϩ stores were normal in OH arteries. Importantly, 100 nM ouabain constricted both control and OH arteries by ϳ26 m, indicating that this response was not downregulated in OH rats. This maximal ouabain-induced constriction corresponds to a ϳ90% increase in resistance to flow in these small arteries; thus ouabain at EC 50 of ϳ0.66 nM should raise resistance by ϳ35%. We conclude that dynamic constriction in response to circulating nanomolar ouabain in small arteries likely makes a major contribution to the increased vascular tone and BP in OH rats. myogenic reactivity; resistance artery OUABAIN, A MAMMALIAN adrenocortical hormone (4,20,21,28), apparently plays an important role in the pathogenesis of hypertension in humans and rodents. About 50% of patients with essential hypertension and a majority of patients with adrenocortical adenomas and hypertension have elevated plasma endogenous ouabain (EO) (42,45). In normal humans, ouabain infusion increases peripheral vascular resistance, reduces blood flow, and elevates blood pressure (BP) (35, 47).Moreover, high-dietary salt increases plasma EO levels in normal men (32).Elevated EO levels are also observed in rats with DOCA-salt hypertension (20), reduced renal mass hypertension (24), and Milan strain hypertension (14). Additionally, the chronic treatment of normal rats and mice with ouabain elevates BP, i.e., ouabain-induced hypertension (OH) (12, 33, 50). Although digoxin, lik...

The Milan hypertensive strain (MHS) rats are a genetic model of hypertension with adducin gene polymorphisms linked to enhanced renal tubular Na(+) reabsorption. Recently we demonstrated that Ca(2+) signaling is augmented in freshly isolated mesenteric artery myocytes from MHS rats. This is associated with greatly enhanced expression of Na(+)/Ca(2+) exchanger-1 (NCX1), C-type transient receptor potential (TRPC6) protein, and sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2) compared with arteries from Milan normotensive strain (MNS) rats. Here, we test the hypothesis that the enhanced Ca(2+) signaling in MHS arterial smooth muscle is directly reflected in augmented vasoconstriction [myogenic and phenylephrine (PE)-evoked responses] in isolated mesenteric small arteries. Systolic blood pressure was higher in MHS (145 ± 1 mmHg) than in MNS (112 ± 1 mmHg; P < 0.001; n = 16 each) rats. Pressurized mesenteric resistance arteries from MHS rats had significantly augmented myogenic tone and reactivity and enhanced constriction to low-dose (1-100 nM) PE. Isolated MHS arterial myocytes exhibited approximately twofold increased peak Ca(2+) signals in response to 5 μM PE or ATP in the absence and presence of extracellular Ca(2+). These augmented responses are consistent with increased vasoconstrictor-evoked sarcoplasmic reticulum (SR) Ca(2+) release and increased Ca(2+) entry, respectively. The increased SR Ca(2+) release correlates with a doubling of inositol 1,4,5-trisphosphate receptor type 1 and tripling of SERCA2 expression. Pressurized MHS arteries also exhibited a ∼70% increase in 100 nM ouabain-induced vasoconstriction compared with MNS arteries. These functional alterations reveal that, in a genetic model of hypertension linked to renal dysfunction, multiple mechanisms within the arterial myocytes contribute to enhanced Ca(2+) signaling and myogenic and vasoconstrictor-induced arterial constriction. MHS rats have elevated plasma levels of endogenous ouabain, which may initiate the protein upregulation and enhanced Ca(2+) signaling. These molecular and functional changes provide a mechanism for the increased peripheral vascular resistance (whole body autoregulation) that underlies the sustained hypertension.

Arterial smooth muscle (ASM) Na+/Ca2+ exchanger type 1 (NCX1) and TRPC/Orai-containing receptor/store-operated cation channels (ROC/SOC) are clustered with α2 Na+ pumps in plasma membrane microdomains adjacent to the underlying junctional sarcoplasmic reticulum. This arrangement enables these transport proteins to function as integrated units to help regulate local Na+ metabolism, Ca2+ signaling and arterial tone. They thus influence vascular resistance and blood pressure (BP). For instance, up-regulation of NCX1 and TRPC6 has been implicated in the pathogenesis of high BP in several models of essential hypertension: ouabain-induced hypertensive rats, Milan hypertensive strain rats, and Dahl salt-sensitive hypertensive rats, which all have elevated plasma ouabain levels. Enhanced expression and function of arterial smooth muscle NCX1 and TRPC/Orai1-containing channels in experimental and clinical hypertension implies that these proteins are potential targets for pharmacological intervention.

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Aim: Although the Innova™ self-expanding nitinol stent (Boston Scientific, Marlborough, MA) exhibits acceptable performance in long-term safety and efficacy when used for the treatment of femoropopliteal (FP) lesions, clinical outcomes following its implantation have not been systematically studied in real-world settings. We investigated the one-year clinical outcomes after implantation of Innova™ self-expanding nitinol stents for the treatment of FP lesions in real-world settings.Methods: In this multicenter study, 481 lesions in 453 consecutive patients with peripheral artery disease (PAD) (74 ± 9 years; male, 70%; diabetes mellitus, 61%; dialysis, 27%; critical limb ischemia, 37%) who underwent endovascular therapy with the implantation of Innova™ self-expanding nitinol stents for FP lesions were analyzed from February 2016 to April 2017. The primary endpoint was one-year restenosis, whereas the secondary endpoints included one-year major adverse limb events and predictors for one-year restenosis.Results: The mean lesion length was 18 ± 10 cm. One-year restenosis and major adverse limb event rates were 36% and 18%, respectively. Multivariate analysis revealed that the presence of diabetes mellitus (odds ratio [OR]: 1.83; 95% confidence interval [CI]: 1.07–3.13), distal reference vessel diameter (OR: 1.86; 95% CI: 1.09–3.16), spot stenting (OR: 2.27; 95% CI: 1.27–4.06), and lack of one-year cilostazol treatment (OR: 0.58; 95% CI: 0.33–1.00) were independent risk factors for one-year restenosis.Conclusion: The current study demonstrated one-year clinical outcomes after Innova™ self-expanding nitinol stent placement for the treatment of FP lesions, including challenging cases in real-world settings.

An 86-year-old nondiabetic woman with an episode of transient ischemic attack two days earlier was referred to our hospital. She had a history of neurogenic bladder and chronic atrial fibrillation and had been anuric for two days. Bubbles were detected by echocardiography in the right atrium, right ventricle, and inferior vena cava. Computed tomography revealed gas accumulation in the wall and lumen of the bladder. She recovered after urinary drainage and antibiotic therapy, and bubbles were no longer detected. It was suspected that bacterial injury of the bladder wall and high intravesical pressure led gas to enter the venous system.

Purpose: To evaluate a new scoring balloon, the non-slip element (NSE) percutaneous transluminal angioplasty (PTA) balloon, in the treatment of femoropopliteal lesions by comparing angiographic dissection patterns to those of a conventional balloon. Methods: This retrospective, single-center study included 71 symptomatic patients (mean age 77.4±8.8 years; 33 men) with de novo femoropopliteal lesions <20 cm long treated with balloon angioplasty between January 2017 and May 2018. Thirty-four patients were treated with 3 inflations of an NSE balloon and 37 patients were treated with a conventional balloon. Results: Severe dissections were fewer (8.8% vs 29.7%, p=0.027) and the total dissection length was shorter (11.5±12.8 vs 35.7±24.1 mm, p=0.027) in the NSE group. The bailout stenting rate was also lower in the NSE group (17.6% vs 40.5%, p=0.035). There were no significant differences between the groups regarding lesion length (70.3±50.4 vs 77.8±56.6 mm, p=0.28), inflation time (294±162 vs 353±179 seconds, p=0.08), or inflation pressure (10.6±5.0 vs 11.3±5.3 atm, p=0.31). Conclusion: Three NSE balloon inflations may reduce severe dissections induced by balloon angioplasty in femoropopliteal lesions.