Estimating the real-world performance of the PROMISE minimal-risk tool.

BACKGROUND: Stable chest pain is a common indication for cardiac catheterization. We assessed the prognostic value of the Prospective Multicenter Imaging Study for Evaluation (PROMISE) Minimal-Risk Tool in identifying patients who are at very low risk of obstructive coronary artery disease (CAD) or downstream cardiovascular adverse outcomes. METHODS: We applied the PROMISE Minimal-Risk Tool to consecutive patients without known CAD who underwent elective cardiac catheterization for stable angina from January 1, 2000 to December 31, 2014 in the Duke Databank for Cardiovascular Disease (DDCD). Patients with scores >0.46 (top decile of lowest-risk from the PROMISE cohort) were classified as low-risk. Logistic regression modeling compared likelihood of freedom from obstructive coronary artery disease on index angiography, 2-year survival, and 2-year survival free of myocardial infarction (MI) and MI/revascularization between low- and non low-risk patients. Alternative cut points to define low- risk patients were also explored. RESULTS: Among 6251 patients undergoing cardiac catheterization for stable chest pain, 1082 (17.3%) were low-risk per the PROMISE minimal-risk tool. Among low risk patients, obstructive coronary artery disease was observed in 14.9% and left main disease (≥ 50% Stenosis) was rare (0.9%). Compared with other patients, low risk patients had a higher likelihood of freedom from obstructive coronary disease on index catheterization (85.1% vs. 44.2%, OR 4.84, 95% CI 4.06-5.77). Low risk patients had significantly higher survival (98.2% vs. 94.4%, OR 3.18, 95% CI 1.99-5.08), MI-free survival (97.2% vs. 91.9%, OR 3.03, 95% CI 2.07-4.45), and MI/revascularization-free survival (86.2 vs. 59.9%, OR 4.19, 95% CI 3.48-5.05) at 2 years than non-low risk patients. Operating characteristics for predicting the outcomes of interest varied modestly depending on the low-risk cut-point used but the positive predictive value for 2 year freedom from death was >98% regardless. CONCLUSION: The PROMISE minimal-risk tool identifies 17% of stable chest pain patients referred to cardiac catheterization as low risk. These patients have a low prevalence of obstructive CAD and better survival than non-low risk patients. While this suggests that these patients are unlikely to benefit from catheterization, further research is needed to confirm a favorable downstream prognosis with medical management alone.

Stereoselective Access to the Core Structure of Macroline-Type Indole Alkaloids: Total Synthesis of Macroline and Alstomicine.

Rapid synthesis of the pentacyclic core structure of macroline-type indole alkaloids, and its application in the total synthesis of macroline and alstomicine is described. The core structure was accomplished in a highly stereocontrolled manner via two key steps, Ireland-Claisen rearrangement and Pictet-Spengler cyclization, commencing from a readily available starting material l-tryptophan, which obviated the need of a particular chiral source as an external catalyst, reagent, or internal auxiliary.

Nazarov Cyclization and Tandem [4 + 2]-Cycloaddition Reactions of Donor-Acceptor Cyclopropanes.

The development of aryl vinyl/divinyl donor-acceptor cyclopropanes (DACs) as novel Nazarov cyclization (NC) precursors is described. The 1,3-zwitterion, generated from DACs embedded in the divinyl framework, acts as a pentadienyl cation, a requisite for Nazarov cyclization. A cyclic allyl cation in the course of NC was trapped with external nucleophiles to provide an interrupted NC product. Indeed, an allyl cation in this reaction is analogous to a 1,4-zwitterion that on reaction with dipolarophiles provided an easy access to substituted pyrans with excellent yield and diastereoselectivity via NC followed by a formal [4 + 2] cycloaddition.

Prevalence and risk factors for left ventricular diastolic dysfunction in a scleroderma cohort.

OBJECTIVES: Left ventricular diastolic dysfunction (LVDD) is more common in systemic sclerosis (SSc) compared to the general population. Focal myocardial ischaemia and fibrosis may be important in its pathogenesis. LVDD is associated with increased mortality and little is known about the risk factors. Advanced SSc lung complications may accompany LVDD. METHOD: We conducted a cross-sectional study of 300 SSc outpatients with and without LVDD, seen between May 2012 and May 2014, and performed univariate and multivariate regression analyses to determine clinical factors associated with LVDD. LVDD was confirmed by the latest echocardiogram (tissue Doppler imaging) reports. Interstitial lung disease (ILD) was confirmed by high-resolution computed tomography (HRCT) and pulmonary hypertension (PH) was diagnosed by right heart catheterization (RHC). RESULTS: Of the 300 SSc patients, there were 133 (44%) with LVDD. In the univariate analysis, advanced age, disease duration (from the onset of Raynaud's phenomenon), anti-centromere antibody, the presence of SSc lung complications, systemic hypertension, smoking, valvular heart disease, chronic kidney and thyroid diseases were all significantly associated with LVDD. However, in the multivariate regression analysis, advanced age was the most significant factor associated with LVDD, followed by systemic hypertension and SSc lung complications. There were significantly more deaths in the LVDD group (p < 0.0001). CONCLUSIONS: LVDD was more prevalent in the SSc population, especially in those with advanced age, systemic hypertension, or SSc-pulmonary complications. SSc patients with pulmonary fibrosis or pulmonary hypertension had more advanced LVDD and higher mortality. More effective therapy is needed to improve the outcome in this population.

Molecular imaging of small animals with a triple-head SPECT system using pinhole collimation.

Pinhole collimation yields high sensitivity when the distance from the object to the aperture is small, as in the case of imaging small animals. Fine-resolution images may be obtained when the magnification is large since this mitigates the effect of detector resolution. Large magnifications in pinhole single-photon emission computed tomography (SPECT) may be obtained by using a collimator whose focal length is many times the radius of rotation. This may be achieved without truncation if the gamma camera is large. We describe a commercially available clinical scanner mated with pinhole collimation and an external linear stage. The pinhole collimation gives high magnification. The linear stage allows for helical pinhole SPECT. We have used the system to image radiolabeled molecules in phantoms and small animals.

Phentolamine mesylate relaxes rabbit corpus cavernosum by a nonadrenergic, noncholinergic mechanism.

The contribution of NO-cGMP dependent pathway to phentolamine mesylate-evoked nonadrenergic, noncholinergic relaxation of rabbit corpus cavernosum was investigated in vitro. Stimulation of nonadrenergic, noncholinergic neurons of the rabbit corpus cavernosum elicited frequency-related relaxation that was significantly attenuated by L-NAME (NO synthase inhibitor) or ODQ (an inhibitor of guanylate cyclase). Moreover, tetrodotoxin, a sodium channel blocker, abolished the electrical field stimulation-induced relaxation of rabbit corpus cavernosum, suggesting that neuronal release of NO mediates relaxation to electrical field stimulation. Phentolamine mesylate (30 and 100 nM) dose-dependently enhanced electrical field stimulation-induced relaxation of the rabbit corpus cavernosum. Prazosin (30 microM) and yohimbine (30 microM) failed to affect phentolamine mesylate-mediated nonadrenergic, noncholinergic rabbit penile smooth muscle relaxation, suggesting that phentolamine relaxes rabbit corpus cavernosum independent of alpha-adrenergic receptor blockade. In contrast, pretreatment of the rabbit cavernosal strips with L-NAME significantly-attenuated electrical field stimulation produced relaxations to phentolamine mesylate, suggesting that phentolamine mesylate relaxes rabbit corpus cavernosum by activating NO synthase. The data suggest that phentolamine mesylate relaxes nonadrenergic noncholinergic neurons of the rabbit corpus cavernosum by activating NO synthase and is independent of alpha-adrenergic receptor blockade.

Sildenafil relaxes rabbit clitoral corpus cavernosum.

The role of phosphodiesterase type 5 inhibition in the modulation of female sexual dysfunction was investigated by assessing its effects on in vitro relaxation of rabbit clitoris. Stimulation of the non-adrenergic, non-cholinergic neurons of the clitorus elicited a frequency-dependent relaxation response. Inhibition of NO synthase with L-NAME (100 microM) or inhibition of soluble guanylate cyclase with ODQ (1.0 microM) almost completely abolished the electrical field stimulation-induced relaxation of clitorus suggesting that NO-cGMP pathway mediates the relaxation response to electrical field stimulation. Similarly, tetrodotoxin, a neuronal sodium channel blocker abolished the electrical field stimulation-induced clitoral relaxation implying a neuronal release of NO contributes to the electrical field stimulation elicited relaxation. Pretreatment of the clitoral corpus cavernosum strips with sildenafil (100 nM) enhanced the electrical field stimulation-induced relaxations both in magnitude and duration. The results suggest that sildenafil enhances electrical field stimulation elicited clitoral relaxation by a NO-cGMP dependent pathway. These data also imply that sildenafil may be useful to treat female sexual dysfunction.

A nontoxic diphtheria toxin analogue inhibits neonatal bladder smooth muscle cell proliferation.

PURPOSE: The response of the neonatal bladder to infravesical obstruction, such as posterior urethral valves or detrusor-sphincter dyssynergia, may result in structural and functional changes that persist well after obstruction is treated. A pharmacological means of inhibiting smooth muscle cell proliferation would likely serve to halt or reverse this deleterious process. Heparin binding (HB) epidermal growth factor (EGF) is a known smooth muscle cell mitogen, while its membrane bound precursor serves as the diphtheria toxin receptor. We report the effects of the nontoxic diphtheria toxin analogue cross reacting material (CRM) 197 on neonatal sheep bladder smooth muscle cell proliferation. MATERIALS AND METHODS: Neonatal sheep smooth muscle cell cultures were obtained from whole bladder explants. Immunohistochemical staining was performed for desmin and alpha-smooth muscle actin. HB-EGF messenger RNA was detected by reverse transcriptase polymerase chain reaction using primers to the human sequence, while pro-HB-EGF peptide was confirmed using a diphtheria toxin sensitivity assay with incorporation of tritiated leucine. Cells grown in 96 well plates were exposed to 1, 10 and 100 microg./ml. CRM 197 for 5 days, after which relative cell number was determined using an 3-[4,5-dimethylthiazol-2-yl] -2,5-diphenyltetrazolium bromide; thiazolyl blue based assay read at a wavelength of 550 nm. Statistical analysis was performed using Student's t test. RESULTS: Primary cell cultures stained positive for desmin and alpha-smooth muscle actin, confirming a smooth muscle origin. Reverse transcriptase polymerase chain reaction yielded a 453 bp product with 88% homology to human HB-EGF. Total protein synthesis significantly decreased when cells were incubated with diphtheria toxin, confirming the presence of membrane bound pro-HB-EGF. CRM 197 inhibited bladder smooth muscle cell growth in a dose dependent fashion at a concentration of 10 microg./ml., resulting in a 40% decrease in proliferation (p <0.0001). CONCLUSION: CRM 197 inhibits bladder smooth muscle cell proliferation in a dose dependent, nontoxic fashion through its interaction with HB-EGF. These data suggest that molecular strategies designed to inhibit HB-EGF mediated cell growth may prove beneficial for the prevention and/or treatment of detrusor hypertrophy secondary to anatomical or functional bladder outlet obstruction.

The incidence of intersexuality in children with cryptorchidism and hypospadias: stratification based on gonadal palpability and meatal position.

PURPOSE: The combined findings of cryptorchidism and hypospadias often indicate the existence of an intersex state. Testicular maldescent and incomplete tubularization of the urethral plate occur in a spectrum with the severity of the 2 processes likely dependent on the degree of pathophysiology in the androgenic hormonal axis. The incidence of intersexuality in children with undescended testes, hypospadias and otherwise nonambiguous male genitalia has been reported to be 27%. Although the likelihood of genotypic or gonadal ambiguity has previously been associated with meatal position in this population, to our knowledge our study is the first to evaluate the incidence of intersexuality relative to whether the undescended testis is palpable or nonpalpable. MATERIALS AND METHODS: The database at our hospital was searched for all cases of undescended testes (2,105) and hypospadias (1,057) between 1982 and 1996. Radiographic, histological and karyotypic data were compiled for all patients presenting with both diagnoses. Gonadal palpability (palpable versus nonpalpable) and meatal position (anterior versus mid versus posterior) were recorded and correlated with the likelihood of identifying an intersex condition. Ten boys with a diagnosis of undescended testes subsequent to inguinal hernial repair were excluded from study. Patients with congenital adrenal hyperplasia or complete testicular feminization were also excluded from study due to the clearly female appearance of the external genitalia. Statistical significance was assessed using Fisher's exact test. RESULTS: We identified 79 patients presenting with undescended testes, hypospadias and a phallus that was believed to be a possible penis. Intersex conditions were identified with nearly equal frequency in the 44 cases of unilateral (30%) and 35 of bilateral (32%) cryptorchidism. In the unilateral undescended testes group patients with a nonpalpable testis were at least 3-fold more likely to have an intersex condition than those with a palpable undescended testis (50 versus 15%, p = 0.02). In the bilateral group patients with 1 or more nonpalpable testes were also nearly 3-fold as likely to have an intersex condition than those with bilateral palpable undescended gonads (47 versus 16%, p = 0.07). Meatal position was graded as anterior in 33% of cases, mid in 25% and posterior in 41% with the more posterior location conferring a significantly greater likelihood of an intersex condition (anterior 2 of 26, mid 1 of 20 and posterior 21 of 33). CONCLUSIONS: Gonadal palpability is an important predictor of an intersex state in unilateral and bilateral cases of cryptorchidism with hypospadias. Patients with an undescended testis that cannot be palpated are significantly more likely to have an intersex condition than those in whom the undescended testis may be palpated on physical examination. The severity of hypospadias likewise has a strong positive correlation with an intersex state.

Effect of centrifuge speed, refrigeration medium, and sperm washing medium on cryopreserved sperm quality after thawing.

Cryopreservation and subsequent thawing of semen for assisted reproductive procedures decreases sperm motility; motility further reduces when the cryoprotectant medium is removed because of the osmotic shock and centrifugation done to prepare the sperm. To compare motility and thus pregnancy rates, this study examined the effects of adding an additional refrigeration medium and three different centrifugation speeds for sperm preparation. Semen samples from 16 healthy normal volunteers were obtained by masturbation after 48 h of abstinence. Sperm motility and other motion characteristics were analyzed with a computer-assisted semen analyzer before freezing, after thawing, and after centrifugation. Each sample was divided into 6 aliquots and frozen using the liquid nitrogen vapor method. After thawing, human tubal fluid (HTF) with 5% human serum albumin was added to 3 aliquots, and refrigeration medium (identical to freezing medium without glycerol) was added to the remaining 3 tubes for each specimen. The tubes containing the two media were then washed by centrifugation at 100 g, 300 g, and 500 g for 10 min. Aliquots with refrigeration medium did not significantly differ from those with HTF for percent motility, curvilinear velocity, straight-line velocity, and amplitude of lateral head displacement at any centrifugation speed. Motile sperm count was significantly greater only at 100 g and 300 g for refrigeration medium (p = .02 and .01) and HTF (p = 0.001); at 300 g, average path velocity in refrigeration medium aliquots (p = .01) and linearity in HTF (p = .01) were greater. The results indicated that the reduction in motility and other motion characteristics probably cannot be overcome by changing factors such as the sperm preparation medium or centrifugation speed. More effective cryopreservation techniques or preparation methods that eliminate centrifugation need to be developed.

Inhibition of platelet adhesion and aggregation by E4021, a type V phosphodiesterase inhibitor, in guinea pigs.

E4021 (sodium 1-[6-chloro-4-(3, 4-methylenedioxybenzyl)-aminoquinazolin-2-yl]piperidine-4-ca rboxylate sesquihydrate) is a highly selective and potent inhibitor of type V phosphodiesterase(PDE5). The in vitro and in vivo effect of E4021 on platelet function was evaluated, using echistatin, a potent disintegrin, as a positive reference agent. E4021 inhibits aggregatory response to collagen in washed human platelets (IC50 = 5 microM, vs. 0.14 microM with echistatin). In the ex vivo-platelet aggregation assay using whole blood from treated guinea pigs, E4021 (9 mg/kg i.v.) showed a moderate inhibition (43%) against collagen (0.125 microg/ml), whereas echistatin (250 microg/kg i.v.) exerted a 88% inhibition. The absence of endothelium-derived factors (NO) may account for the moderate in vitro and ex vivo antiplatelet activity of E4021. In an in vivo model of reversible platelet aggregation elicited by collagen (100 microg/kg i.v.), both E4021 and echistatin attenuated the intrapulmonary platelet accumulation in guinea pigs (-36% and -44%, respectively). In addition, E4021 (9 mg/kg i.v.) and echistatin (250 microg/kg i.v.) caused a similar inhibition of platelet adhesion at sites of microfilament-induced vascular injury in guinea pigs (52% and 65%, respectively). The two agents in combination did not show additive effect, suggesting that E4021 inhibits platelet activation and impairs interactions of adhesion receptors with matrix proteins. E4021 caused a selective increase in cGMP concentrations in the platelets isolated from treated guinea pigs: cAMP was not affected. It is concluded that the antiplatelet activity of E4021 is mediated through cGMP mechanism by virtue of selective inhibition of PDE5 in the platelets.

Antiplatelet and antiproliferative effects of SCH 51866, a novel type 1 and type 5 phosphodiesterase inhibitor.

SCH 51866 is a potent and selective PDE1 and PDE5 inhibitor. The antiplatelet, antiproliferative, and hemodynamic effects of SCH 51866 were compared with those of E4021, a highly selective PDE5 inhibitor. SCH 51866 inhibited PDE1 and PDE5 isozymes with a 50% inhibitory concentration (IC50) of 70 and 60 nM, respectively. SCH 51866 and E4021 inhibited washed human platelet aggregation induced by collagen with an IC50 of 10 and 4 microM, respectively, and attenuated (p < 0.05) the adhesion of 111indium-labeled platelets to the nylon filament-injured rat aorta. The doses of SCH 51866 and E4021 that inhibited platelet adhesion caused significant increases in platelet cyclic guanosine monophosphate (cGMP; p < 0.05). SCH 51866 (1-10 mg/kg, p.o. twice daily) but not E4021 (3-30 mg/kg, p.o twice daily) inhibited neointima formation in the carotid arteries of spontaneously hypertensive rats (SHRs) subjected to balloon angioplasty. Moreover, SCH 51866 (0.3-10 mg/kg, p.o.) elicited dose-dependent reduction in blood pressure in SHRs, whereas E4021 (3-30 mg/kg, p.o.) did not affect blood pressure in SHRs. In conclusion, the data suggest that inhibition of PDE1 and PDE5 isozymes by SCH 51866 exerts antiplatelet and vascular protective effects. In comparison, inhibition of PDE5 alone by E4021 exhibited antiplatelet effects without affecting neointima formation.

In vivo inhibition of platelet adhesion by a cGMP-mediated mechanism in balloon catheter injured rat carotid artery.

The role of cyclic guanosine monophosphate (cGMP) versus cyclic adenosine monophosphate (cAMP) mediated mechanism in modulating platelet adhesion was investigated in balloon catheter injured rat carotid arteries. Vascular injury with balloon angioplasty significantly increased the adherence of platelets to the injured carotid arteries. Intravenous infusion of zaprinast (1 mg/kg/min), a cGMP phosphodiesterase inhibitor, or sodium nitroprusside (8 micrograms/kg/min), a stimulator of soluble guanylate cyclase, significantly attenuated the adherence of platelets to the injured carotid arteries. In comparison, infusion of milrinone, a cAMP phosphodiesterase inhibitor, or 8-bromo-cAMP failed to affect the platelet deposition in the injured carotid arteries. Nifedipine or aspirin also failed to attenuate the adherence of platelets to the injured carotid arteries. In conclusion, agents known to elevate intracellular platelet cGMP but not cAMP appear to afford the most effective protection in vivo against the adhesion of platelets to the vessel wall without intact endothelium.

Phosphoramidon does not inhibit endogenous endothelin-1 release stimulated by hemorrhage, cytokines and hypoxia in rats.

The role of phosphoramidon-sensitive endothelin converting enzyme in the release of endogenous endothelin-1 was investigated in anesthetized rats. Intravenous infusion of phosphoramidon 0.3 mg/kg/min did not suppress the release of endothelin-1 stimulated by hemorrhage or cytokines. Elevation of endothelin-1 in rats subjected to hypoxia was not modified by phosphoramidon (0.1 or 0.3 mg/kg/min for 2 h). A high dose of phosphoramidon (10 mg/kg i.v. +0.1 mg/kg/min) significantly potentiated the hypoxia-induced increases in plasma endothelin-1 levels. Increases in endothelin-1 release caused by bilateral nephrectomy were further enhanced by hypoxia. It is concluded that the release of endogenous endothelin-1 release stimulated by hemorrhage, cytokines and hypoxia is resistant to inhibition by phosphoramidon, and at high doses, phosphoramidon potentiates hemorrhage- and hypoxia-induced increases in endothelin-1 levels, most likely by preventing its degradation.

Inhibition of endothelial derived relaxing factor (EDRF) aggravates ischemic acute renal failure in anesthetized rats.

The relative importance of endothelial derived relaxing factor (EDRF)/nitric oxide (NO) in maintaining kidney function in normal condition and in acute renal failure (ARF) were evaluated in inactin anesthetized rats. ARF was induced by unilateral occlusion of the left renal artery (40 min) followed by reperfusion, with the contralateral kidney serving as normal control. This protocol resulted in marked reductions in renal plasma flow (RPF), glomerular filtration rate (GFR) and increases in fractional sodium excretion (FENa) and urinary protein excretion in the post-ischemic kidney in comparison to the contralateral normal kidney. Administration of the nitric oxide (NO) synthase inhibitor NG--monomethyl-L-arginine (0.25 mg/kg per min, L-NMMA) exacerbated the ischemia-induced changes in renal functions as reflected by further reductions in urine flow (V), GFR, marked sodium wasting and renal edema. Pretreatment of the animals with NO precursor L-arginine (2.5 mg/kg per min, L-Arg) abolished the detrimental effects of L-NMMA in ARF. In contrast, D-Arginine (2.5 mg/kg per min, D-Arg) failed to reverse the detrimental effects of L-NMMA. Infusion of L-Arg alone also resulted in improvements in RPF and GFR in the ischemic kidney. The results of the present study suggest that the function of the ischemic kidney is sustained by EDRF/NO and is thus more sensitive to NO synthase inhibition.

Attenuation of ischemic acute renal failure by phosphoramidon in rats.

The protective effects of phosphoramidon, a dual inhibitor of endothelin-converting enzyme and neutral endopeptidase (E.C. 24.11), on renal function in ischemic acute renal failure were investigated in anesthetized rats. Intravenous infusion of phosphoramidon (0.03 and 0.1 mg/kg per min) significantly suppressed tubular sodium wasting (measured by fractional excretion of sodium) and proteinuria in the postischemic kidney without modifying functional parameters in the contralateral normal kidney. Phosphoramidon (0.1 mg/kg/min) was associated with increased glomerular filtration in the ischemic kidney. In comparison, SCH 42354, a highly selective inhibitor of neutral endopeptidase at 0.3 mg/kg/min, did not inhibit endothelin-converting enzyme or afford renal protection. The data suggest that the protective action of phosphoramidon against ischemic acute renal failure is most likely mediated by inhibition of endothelin formation.

Atrial natriuretic factor potentiating and hemodynamic effects of SCH 42495, a new, neutral metalloendopeptidase inhibitor.

Neutral metalloendopeptidase (NEP) inhibitors delay atrial natriuretic factor (ANF) catabolism and potentiate biological responses to ANF. We describe biochemical and pharmacological profiles of a novel NEP inhibitor, SCH 42354 (N-[2(S)-(mercaptomethyl)-3-(2-methylphenyl)-4-oxopropyl]-L-methionine and its orally active ethylester prodrug, SCH 42495. SCH 42354 selectively inhibited hydrolysis of leu-enkephalin and ANF (IC50 of 8.3 and 10.0 nmol/L, respectively) in vitro. Plasma levels of exogenous ANF were augmented and ANF clearance from plasma was delayed by oral SCH 42495 (3 to 30 mg/kg) in normotensive rats. Plasma ANF levels in volume expanded rats were higher in SCH 42495-treated rats. Diuretic and natriuretic effects of ANF were increased in rats treated with SCH 42495. Oral doses of 1, 3, or 10 mg/kg of SCH 42495 produced significant reductions in blood pressure in DOCA-Na hypertensive rats of 22 +/- 6, 43 +/- 7, and 62 +/- 12 mm Hg, respectively, which were not associated with increases in heart rate. These doses did not alter urine flow, salt excretion, or plasma ANF. SCH 42495 produced significant elevation of urinary excretion of ANF and cGMP. In Dahl-S hypertensive rats, SCH 42495 (1 to 10 mg/kg orally) produced falls in blood pressure of a magnitude similar to that observed in DOCA-Na hypertensive rats. Significant hypotensive activity was observed 18 h after a single 10 mg/kg oral dose in Dahl-S hypertensive rats. In DOCA-Na hypertensive rats, a single dose of SCH 42495 significantly decreased cardiac output and did not lower systemic vascular resistance, a profile similar to that of ANF. The hypotensive response to SCH 42495 was not ascribable to ACE inhibition. Pithed rat preparations revealed no interaction of the drug with autonomic cardiovascular function. The antihypertensive effect of SCH 42495 likely results from potentiation of endogenous ANF via NEP inhibition.

Disparate effects of phosphoramidon on blood pressure in SHR and DOCA-salt hypertensive rats.

Phosphoramidon inhibits both endothelin converting enzyme (ECE) and neutral metalloendopeptidase (NEP). The contribution of ECE and NEP inhibition to the antihypertensive effects of phosphoramidon was investigated in SHR and DOCA-salt hypertensive rats. SCH 32615, an active acid of the potent and selective NEP inhibitor prodrug SCH 34826 was used as a reference compound. Intravenous infusion of SCH 32615 (1.0 mg/kg/min x 2 hr) or phosphoramidon (0.3 and 1.0 mg/kg/min x 2 hr) did not reduce blood pressure (BP) in conscious SHR. The combination of SCH 32615 (100 mg/kg + 1.0 mg/kg/min) and phosphoramidon (0.3 mg/kg/min) also did not alter BP in SHR. In comparison, the BP of conscious DOCA-salt rats was significantly reduced by phosphoramidon (0.01, 0.1 and 1.0 mg/kg/min x 2 hr) (-28 +/- 6, -51 +/- 5 and -85 +/- 6 mmHg, respectively). SCH 32615 (100 mg/kg, i.v.) over 5 min followed by a sustained infusion of 1.0 mg/kg/min for 2 hr also reduced BP by 49 +/- 7 mmHg (P < .05) in DOCA-salt rats. However, phosphoramidon (0.1 mg/kg/min x 2 hr) failed to cause a further reduction in BP in DOCA-salt rats concurrently receiving SCH 32615. In contrast, a higher dose of phosphoramidon (0.3 mg/kg/min) in combination with SCH 32615 caused a greater reduction in BP in DOCA-salt rats than SCH 32615 alone. In anesthetized normotensive rats, phosphoramidon (0.01-1.0 mg/kg/min x 30 min) dose-dependently inhibited the BP responses to big endothelin-1 (BET-1) without blocking the pressor responses to ET-1. SCH 32615 failed to attenuate the pressor responses to either BET-1 or ET-1. The results indicate that SCH 32615 lacks in vivo ECE inhibitory activity. It is concluded that the antihypertensive action of SCH 32615 and low doses of phosphoramidon can be attributed to the inhibition of NEP which may presumably cause an accumulation of ANF. In comparison, at higher doses phosphoramidon causes a further reduction of BP in DOCA-salt hypertensive rats by inhibition of endothelin bioconversion.

Phosphoramidon abolishes the increases in endothelin-1 release induced by ischemia-hypoxia in isolated perfused guinea pig lungs.

Endothelin (ET)-1 is a potent vasoactive peptide elaborated by the vascular endothelial cells. In the present study we examined the effects of ischemia-hypoxia (I/H) on ET-1 release from isolated perfused guinea pig lungs and heart. Guinea pig lungs subjected to 15 min I/H followed by reperfusion and reventilation significantly (P less than .05) augmented ET-1 release from 14.1 +/- 2.7 to 30.4 +/- 5.6, 27.3 +/- 4.0 and 28.0 +/- 5.0 pg/g of dry weight of lung at 15, 30 and 45 min after I/H, respectively. Pretreatment of guinea pigs with phosphoramidon (10 mg/kg i.v.), an ET converting enzyme inhibitor, 10 min before the removal of lungs abrogated the I/H-induced increases in ET-1 release without affecting the base-line values of ET-1. Phosphoramidon also attenuated the elevations in pulmonary insufflation pressure (PIP) produced by I/H. Moreover, infusion of big ET-1 (BET-1; 30 micrograms/over 15 min) into isolated perfused guinea pig lungs enhanced PIP that was abolished by phosphoramidon. Isolated guinea pig hearts subjected to 15 or 30 min of global ischemia exhibited no disturbances in ET-1 release or mechanical activity. In addition, the increases in perfusion pressure elicited by BET-1 infusion (12 micrograms/over 30 min) into isolated guinea pig hearts was unaffected by phosphoramidon. In a separate study in anesthetized guinea pigs, phosphoramidon significantly attenuated the increases in blood pressure and PIP elicited by BET-1 (10 micrograms/kg i.v.); the pressor and PIP responses to ET-1 (4 micrograms/kg i.v.) were not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathoadrenal stimulation, not endothelin, plays a role in acute pressor response to cyclosporine in anesthetized rats.

The possible role of sympathoadrenal stimulation and endothelin release in cyclosporine (CS)-induced hypertension was ascertained in intact and pithed rats. CS (20 and 40 mg/kg), administered by i.v. infusion over 10 min, produced a dose-dependent increase in blood pressure: 19 +/- 5 and 31 +/- 2 mm Hg in intact rats and 13 +/- 4 and 18 +/- 2 mm Hg in pithed rats. In intact rats, pretreatment with reserpine (5 mg/kg, i.p.) or hexamethonium (10 mg/kg, i.v.) greatly blunted the pressor responses to CS (40 mg/kg) (7 +/- 3 and 11 +/- 2 mm Hg, respectively). In pithed rats, the blood pressure responses to CS (40 mg/kg) were significantly impaired, but were not further modified by phenoxybenzamine (3 mg/kg, i.v.), whereas adrenalectomy completely abolished the CS-induced pressor responses (0 +/- 1 mm Hg). CS (40 mg/kg) did not potentiate pressor responses to sympathetic nerve stimulation (0.1 and 0.3 Hz) or vasoconstrictors, including angiotensin II (0.03 microgram/kg, i.v.), phenylephrine (1 microgram/kg, i.v.) and arginine vasopressin (0.075 microgram/kg) in pithed rats. In addition, CS (40 mg/kg, i.v.) did not cause elevation of plasma immunoreactive endothelin-1 and -3. Furthermore, phosphoramidon (0.25 mg/kg/min x 30) abolished pressor response to big endothelin-1 (5 micrograms/kg, i.v.) but failed to affect CS-induced hypertension. It is concluded that the acute blood pressure response to CS manifests great dependence on sympathetic nervous system but appears independent of endothelin release.