Identification of peptide sequences that selectively bind to pentaerythritol trinitrate hemisuccinate-a surrogate of PETN, via phage display technology.

The present research investigates the identification of amino acid sequences that selectively bind to a pentaerythritol tetranitrate (PETN) explosive surrogate. Through the use of a phage display technique and enzyme-linked immunosorbent assays (ELISA), a peptide library was tested against pentaerythritol trinitrate hemisuccinate (PETNH), a surrogate of PETN, to screen for those with amino acids having affinity toward the explosive. The results suggest that the library contains peptides selective to PETNH. Following three rounds of panning, clones were picked and tested for specificity toward PETNH. ELISA results from these samples show that each phage clone has some level of selectivity for binding to PETNH. The peptides from these clones have been sequenced and shown to contain certain common amino acid segments among them. This work represents a technological platform for identifying amino-acid sequences selective toward any bio-chem analyte of interest.

Accurate quantitation of pentaerythritol tetranitrate and its degradation products using liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

After an explosion of pentaerythritol tetranitrate (PETN), its degradation products pentaerythritol trinitrate (PETriN), dinitrate (PEDiN) and mononitrate (PEMN) were detected using liquid chromatography-atmospheric-pressure chemical-ionization-mass spectrometry (LC-APCI-MS). Discrimination between post-explosion and naturally degraded PETN could be achieved based on the relative amounts of the degradation products. This information can be used as evidence when investigating a possible relationship between a suspect and a post-explosion crime scene. The present work focuses on accurate quantitation of PETN and its degradation products, using PETriN, PEDiN and PEMN standards specifically synthesized for this purpose. With the use of these standards, the ionization behavior of these compounds was studied, and a quantitative method was developed. Quantitation of PETN and trace levels of its degradation products was shown to be possible with accuracy between 85.7% and 103.7% and a precision ranging from 1.3% to 11.5%. The custom-made standards resulted in a more robust and reliable method to discriminate between post-explosion and naturally-degraded PETN.

Cross-linking of serine racemase dimer by reactive oxygen species and reactive nitrogen species.

Serine racemase (SR) is the only identified enzyme in mammals responsible for isomerization of L-serine to D-serine, a coagonist at N-methyl-D-aspartate (NMDA) receptors in the forebrain. Our previous data showed that an apparent SR dimer resistant to sodium dodecyl sulfate and ß-mercaptoethanol was elevated in microglial cells after proinflammatory activation. Because the activation of microglia is typically associated with an oxidative burst, oxidative cross-linking between SR subunits was speculated. In this study, an siRNA technique was employed to confirm the identity of this SR dimer band. The oxidative species potentially responsible for the cross-linking was investigated with recombinant SR protein. The data indicate that nitric oxide, peroxynitrite, and hydroxyl radical were the likely candidates, whereas superoxide and hydrogen peroxide per se failed to contribute. Furthermore, the mechanism of formation of SR dimer by peroxynitrite oxidation was studied by mass spectrometry. A disulfide bond between Cys6 and Cys113 was identified in 3-morpholinosydnonimine hydrochloride (SIN-1)-treated SR monomer and dimer. Activity assays indicated that SIN-1 treatment decreased SR activity, confirming our previous conclusion that noncovalent dimer is the most active form of SR. These findings suggest a compensatory feedback in which the consequences of neuroinflammation might dampen D-serine production to limit excitotoxic stimulation of NMDA receptors.

Bioactivation of pentaerythrityl tetranitrate by mitochondrial aldehyde dehydrogenase.

Mitochondrial aldehyde dehydrogenase (ALDH2) contributes to vascular bioactivation of the antianginal drugs nitroglycerin (GTN) and pentaerythrityl tetranitrate (PETN), resulting in cGMP-mediated vasodilation. Although continuous treatment with GTN results in the loss of efficacy that is presumably caused by inactivation of ALDH2, PETN does not induce vascular tolerance. To clarify the mechanisms underlying the distinct pharmacological profiles of GTN and PETN, bioactivation of the nitrates was studied with aortas isolated from ALDH2-deficient and nitrate-tolerant mice, isolated mitochondria, and purified ALDH2. Pharmacological inhibition or gene deletion of ALDH2 attenuated vasodilation to both GTN and PETN to virtually the same degree as long-term treatment with GTN, whereas treatment with PETN did not cause tolerance. Purified ALDH2 catalyzed bioactivation of PETN, assayed as activation of soluble guanylate cyclase (sGC) and formation of nitric oxide (NO). The EC(50) value of PETN for sGC activation was 2.2 ± 0.5 µM. Denitration of PETN to pentaerythrityl trinitrate was catalyzed by ALDH2 with a specific activity of 9.6 ± 0.8 nmol · min(-1) · mg(-1) and a very low apparent affinity of 94.7 ± 7.4 µM. In contrast to GTN, PETN did not cause significant inactivation of ALDH2. Our data suggest that ALDH2 catalyzes bioconversion of PETN in two distinct reactions. Besides the major denitration pathway, which occurs only at high PETN concentrations, a minor high-affinity pathway may reflect vascular bioactivation of the nitrate yielding NO. The very low rate of ALDH2 inactivation, presumably as a result of low affinity of the denitration pathway, may at least partially explain why PETN does not induce vascular tolerance.

Differential effects of organic nitrates on endothelial progenitor cells are determined by oxidative stress.

OBJECTIVE: Reduced levels and impaired function of endothelial progenitor cells (EPCs) foster development and progression of atherosclerotic lesions. Endothelial nitric oxide synthase (eNOS)-derived NO regulates EPC mobilization and function. Organic nitrates release NO, and therefore may favorably affect EPC biology. METHODS AND RESULTS: We compared the effects of 2 different nitrates on circulating EPC numbers and function. Treatment of rats with pentaerythritol-trinitrate (PETriN) or isosorbide dinitrate (ISDN) increased circulating EPC levels. EPC from ISDN- but not PETriN-treated animals displayed impaired migratory capacity and increased reactive oxygen species formation in EPCs. In vitro treatment with ISDN reduced migration and incorporation of human EPCs into vascular structures on matrigel, whereas PETriN improved EPC function. ISDN, but not PETriN, increased NADPH oxidase-mediated oxidative stress in cultured human EPCs. Addition of polyethylene-glycolated superoxide dismutase or diphenyliodonium normalized both ISDN-induced superoxide anion production and impaired migratory capacity of EPCs. CONCLUSIONS: Long-acting nitrates increase levels of circulating EPCs, but differ in their effects on EPC function dependent on the induction of intracellular oxidative stress. Organic nitrates that improve EPC function may confer long-term cardiovascular protection based on their beneficial effects on EPC biology.

[Silica-containing urinary stones--clinical issues to keep in mind]. / Silikathaltige Harnsteine im Klinikalltag. Was gibt es zu beachten?

Formation of calculi in efferent urinary passages is always due to supersaturation of urinary calculi substances and associated increased crystallization. Apart from the typical calculi, consisting of calcium oxalate, inorganic phosphates, uric acid or cystine, there are occasional signs of rare substance classes. Although more than 50 silicate stones have already been reported internationally, this stone entity remains relatively unknown. In particular, the occurrence of silicate stones in the absence of magnesium trisilicate abuse is extremely rare. A medium-sized left-sided ureterolith was removed from a 54-year-old male patient using a ureteroscope. X-ray diffraction showed it to be a compound stone consisting of 40% silicate. The patient, who in 1986 was living close to the nuclear reactor accident in Chernobyl, showed no signs of a constant uptake of magnesium trisilicate. However, he had undergone partial (2/3) gastrectomy 4 months before for a drug-refractory gastric ulcer, which had been diagnosed at the end of the 1980s and treated with excessive dosages of a magnesium trisilicate antacid preparation until the time of the operation. The patient had also been suffering from unstable angina pectoris since 1986 and treated with Pentalong (pentaerythrityltetranitrate) for 17 years. We were also able to detect silicium dioxide in components of this drug using X-ray diffraction. Silicate uroliths are extremely rare but they can be clearly identified by X-ray diffraction or infrared spectroscopy and distinguished from artifacts or quartz pebbles. Formation of calculi can be prevented by increasing diuresis as well as switching to a different drug and reducing the dosage.

[Therapy with NO donors-antiatherogenic and antioxidant actions]. / Therapie mit NO-Donatoren. Desiderat einer antiarteriosklerotischen und antioxidativen Therapie.

Nitric acid esters such as glyceryl trinitrate were introduced into therapy more than a century ago and are still widely used for the treatment of myocardial ischemia and its main symptom angina pectoris. The basic mechanisms responsible for the vasodilatory and anti-ischemic action of organic nitrates involve bioactivation of, and nitric oxide (NO) release from, these compounds which have therefore been termed NO donors. The organic nitrate pentaerythritol tetranitrate (PETN) is known to possess antioxidant properties that are thought to be the underlying cause for its specific pharmacological profile. In contrast to other long-acting nitrates, PETN induces tolerance- free vasodilation in humans and was reported to prevent endothelial dysfunction as well as atherogenesis in cholesterol- fed rabbits. However, the exact nature of the vasoprotective signaling pathways triggered by PETN has remained obscure. The present study demonstrates that the active PETN metabolite PETriN stimulates protein expression of the antioxidant defense protein heme oxygenase-1 (HO-1; Figures 1 and 2). Additionally, PETriN enhanced the enzymatic activity of HO-1 measured as formation of the HO-1 metabolites bilirubin (Figure 3) and carbon monoxide (Figure 4) in lysates from endothelial cells. HO-1 induction subsequently led to a marked increase in protein expression of a second antioxidant protein, ferritin, via the HO-1-dependent release of free iron from endogenous heme sources (Figures 1 and 5). Pretreatment of endothelial cells with PETriN was followed by increased cellular resistance to oxidant injury mediated by hydrogen peroxide (Figure 6). Endothelial protection by PETriN was mimicked by exogenous bilirubin which led to an almost complete reversal of hydrogen peroxide-induced toxicity (Figure 8). Increased HO-1 and ferritin expression as well as endothelial protection occurred at micromolar concentrations of PETriN which are well within the range of plasma or tissue levels that can be expected during oral therapy. The capacity to protect the endothelium in vitro may translate into and explain the previously observed antiatherogenic actions of PETN in vivo. In this study, another long-acting nitrate, isosorbide dinitrate (ISDN), did not protect endothelial cells from oxidant damage (Figure 6). The absence of significant cytoprotection in the presence of ISDN was paralleled by a lack of HO-1 and ferritin stimulatory capacity (Figures 2 and 5). ISDN had no significant effect on carbon monoxide release or bilirubin formation (Figures 3 and 4). These observations are in agreement with results demonstrating small or nondetectable amounts of NO released from ISDN and its active metabolite isosorbide mononitrate (ISMN) measured as cyclic GMP formation in RFL-6 reporter cells (Figure 7). Interestingly and in contrast to PETN, isosorbide nitrates are known to induce tolerance to their cardiovascular effects, presumably via oxidant stress. Moreover, in earlier investigations aimed at assessing the antiatherogenic potential of nitrates, PETN but not isosorbide nitrates prevented plaque formation and endothelial dysfunction in animal models of atherosclerosis. Thus, the ability to activate HO-1 induction and associated antioxidant pathways apparently distinguishes PETN from other long-acting nitrates and may explain their different patterns of action in vivo (Figure 9).

Endothelial protection by pentaerithrityl trinitrate: bilirubin and carbon monoxide as possible mediators.

Pentaerithrityl tetranitrate (PETN) is a long-acting donor of nitric oxide (NO) and has recently been characterized as an antianginal agent that, in contrast with other nitric acid esters, does not induce oxidative stress and is therefore free of tolerance. Moreover, animal experiments have revealed that PETN actively reduces oxygen radical formation in vivoand specifically prevents atherogenesis and endothelial dysfunction. Because heme oxygenase-1 (HO-1) has been described as an antiatherogenic and cytoprotective gene in the endothelium, our aim was to investigate the effect of the active PETN metabolite pentaerithrityl trinitrate (PETriN) on HO-1 expression and catalytic activity in endothelial cells. Endothelial cells derived from human umbilical vein were incubated with PETriN (0.01-1 mM) for 8 hr. PETriN increased HO-1 mRNA and protein levels in a concentration-dependent fashion up to 3-fold over basal levels. Elevation of HO-1 protein was accompanied by a marked increase in catalytic activity of the enzyme as reflected by enhanced formation of both carbon monoxide and the endogenous antioxidant, bilirubin. Pretreatment of endothelial cells with PETriN or bilirubin at low micromolar concentrations protected endothelial cells from hydrogen peroxide-mediated toxicity. HO-1 induction and endothelial protection by PETriN were not mimicked by isosorbide dinitrate, another long-acting nitrate. The present study demonstrates that the active PETN metabolite, PETriN, stimulates mRNA and protein expression as well as enzymatic activity of the antioxidant defense protein, HO-1, in endothelial cells. Increased HO-1 expression and ensuing formation of bilirubin and carbon monoxide may contribute to and explain the specific antioxidant and antiatherogenic actions of PETN.

Heme oxygenase-1 induction may explain the antioxidant profile of pentaerythrityl trinitrate.

The organic nitrate pentaerythrityl tetranitrate (PETN) is known to exert long-term antioxidant and antiatherogenic effects by as yet unidentified mechanisms. In cultured endothelial cells derived from human umbilical vein, the active PETN metabolite PETriN (0.01-1 mM) increased heme oxygenase (HO)-1 mRNA and protein levels in a concentration-dependent fashion. HO-1 induction was accompanied by a marked increase in catalytic activity of the enzyme as reflected by enhanced formation of carbon monoxide and bilirubin. Pretreatment with PETriN or bilirubin at low micromolar concentrations protected endothelial cells from hydrogen peroxide-mediated toxicity. HO-1 induction and endothelial protection by PETriN were not mimicked by isosorbide dinitrate, another long-acting nitrate. The present study demonstrates that PETriN stimulates mRNA and protein expression as well as enzymatic activity of the antioxidant defense protein HO-1 in endothelial cells. Increased HO-1 expression and ensuing formation of cytoprotective bilirubin may contribute to and explain the specific antioxidant and antiatherogenic actions of PETN.

[Quantitative gas chromatography-mass spectrometry determination of pentaerythrityl tetranitrate metabolites pentaerythrityl trinitrate, pentaerythrityl dinitrate and pentaerythrityl in human plasma]. / Quantitative gaschromatographische/massenspektrometrische Bestimmung der Pentaerithrityltetranitrat-Metaboliten Pentaerithrityltrinitrat, Pentaerithrityldinitrat und Pentaerithritylmononitrat in Humanplasma.

Assay methods based on gas chromatography/mass spectroscopy (GC-MS) may be used to measure PE1N (pentaerithrityl mononitrate, CAS 1607-00-7), PE2N (pentaerithrityl dinitrate, CAS 1607-01-8) and intermediate pentaerithrityltrinitrate (PE3N, CAS 1607-17-6) in human plasma. Based on this method a simplified method to quantify the metabolites of PETN (pentaerithrityl tetranitrate, CAS 78-11-5, Pentalong) is described. In the present study a consistent method to extract the metabolites of human plasma and following derivatisation is described. Since PE1N can be quantified up to 150 ng/ml, PE2N and PE3N up to 30 ng/ml in human plasma, a dilution of the plasma samples can be avoided. The mean recovery rate is not so high as in other described methods, and inaccuracy is about 10%. Therefore a calibration range between 0.2-30 ng/ml of PE2N and 1-150 ng/ml of PE1N has to be considered. The described method offers an alternative and applicable option to quantify the PETN-metabolites and elucidate their part as NO-donors.

The antioxidant defense protein ferritin is a novel and specific target for pentaerithrityl tetranitrate in endothelial cells.

The organic nitrate pentaerithrityl tetranitrate (PETN) is known to exert long-term antioxidant and antiatherogenic effects by as yet unidentified mechanisms. In porcine aortic endothelial cells, a 24 h incubation with PETN (1-100 microM) or its metabolite pentaerithrityl trinitrate (PETriN) increased levels of the antioxidant protein ferritin up to three-fold over basal, whereas isosorbide dinitrate and isosorbide-5-mononitrate were without significant effect under these conditions. PETriN-induced ferritin expression was blocked by the NO scavenger PTIO but remained unaltered in the presence of ODQ, an inhibitor of soluble guanylyl cyclase. 8-Bromo cyclic GMP and dibutyryl cyclic GMP did not influence basal ferritin synthesis. The iron chelator desferrioxamine abolished ferritin induction by PETriN. Our results show that PETN or its active metabolite PETriN induce ferritin synthesis through NO- and iron-dependent but cyclic GMP-independent pathways. Increased activity of ferritin may contribute to, and at least in part explain, the specific antiatherogenic and antioxidant action of PETN.

Effects of nonintermittent treatment of rabbits with pentaerythritol tetranitrate on vascular reactivity and superoxide production.

Pentaerythritol tetranitrate is an organic nitrate ester that undergoes metabolization to pentaerythritol, pentaerythritol trinitrate, pentaerythritol dinitrate and pentaerythritol mononitrate. Recent data suggested that pentaerythritol tetranitrate is endowed with vasoprotective activities in experimental atherosclerosis. This study was undertaken to gain insight into the underlying mechanism. The basic mechanism of action of all pentaerythritol nitrates was evaluated by measuring liberation of nitric oxide (NO), stimulation of human soluble guanylate cyclase and vasorelaxation in rabbit aorta. A subsequent in vivo study in New Zealand White rabbits was performed to investigate the effects of a 4 months lasting nonintermittent oral treatment with 6 mg pentaerythritol tetranitrate kg(-1) day(-1) on vascular superoxide production, endothelium dependent vasorelaxation and vasorelaxation to pentaerythritol tetranitrate itself. The formation rates of NO from the pentaerythritol nitrates (100 microM, n = 5) in presence of 5 mM cystein were (in nM min(-1)): 62.1 +/- 3.2 (pentaerythritol tetranitrate), 21.3 +/- 0.9 (pentaerythritol trinitrate), 6.4 +/- 0.6 (pentaerythritol dinitrate) and 3.2 +/- 0.4 (pentaerythritol mononitrate). Similarly, the pD2 values (-log M) for half-maximal activation of soluble guanylate cyclase decreased from pentaerythritol tetranitrate (3.391 +/- 0.09, n = 4) to pentaerythritol mononitrate (2.655 +/- 0.04, n = 3) as did the pD2 values (in -log M) for half-maximal relaxation of rabbit aortic rings (n = 7) from pentaerythritol tetranitrate (8.3 +/- 0.17) to pentaerythritol mononitrate (5.0 +/- 0.11). Significant correlations were found between the NO formation rates and the pD2 values for enzyme stimulation (r = 0.98, P = 0.002) and vasorelaxation (r = 0.90, P = 0.049) suggesting that these effects of the pentaerythritol nitrates were mediated by NO. The results of the in vivo study showed that aging induces a significant increase of aortic superoxide production (median values, n = 10) from 2.45 nM mg(-1) min(-1) (age 7 months) to 3.39 nM mg(-1) min(-1) (age 11 months, P < 0.01) that was prevented by concurrent treatment with pentaerythritol tetranitrate (2.76 nM mg(-1) min(-1)). In vitro vasorelaxation to pentaerythritol tetranitrate was identical in all groups indicating absence of nitrate tolerance. Endothelium-dependent vasorelaxation was also identical in all groups. These data suggest that oral treatment with pentaerythritol tetranitrate reduces vascular oxidant stress by an NO-dependent pathway, which may contribute to the vasoprotective activity of pentaerythritol tetranitrate in experimental atherosclerosis.

Impairment of endothelium-dependent vasorelaxation in experimental atherosclerosis is dependent on gender.

OBJECTIVE: Nitric oxide (NO) has been suggested to have antiatherosclerotic effects. It has also been demonstrated that there is a greater basal release of endothelium derived relaxing factor (EDRF) in female as compared to male rabbit aorta, which also might have beneficial effects in atherosclerosis. We thus sought to determine if gender influences the severity of atherosclerosis. METHODS: We studied 18 female and 18 male New Zealand White rabbits that were randomly divided in two groups of 9 animals each and fed either a standard or a cholesterol diet (0.75%) for 15 weeks. RESULTS: In cholesterol-fed rabbits the percentage of atherosclerotic lesions in the aorta was identical in females and males and was inversely correlated with the maximal aortic relaxation to acetylcholine as assessed in organ chamber experiments (females: P < 0.0008, males: P < 0.0002). Importantly, the cholesterol diet induced a significantly (P < 0.025) more severe impairment of maximal vasorelaxation to acetylcholine in males from 78.4 +/- 1.2% to 29.4 +/- 10.2%) compared to females (from 84.4 +/- 1.2% to 60.7 +/- 8.5%). Both male gender (P < 0.0001) and the extent of impairment of endothelium-dependent relaxation (P < 0.0002) were associated with a reduced aortic sensitivity to S-nitroso-N-acetyl-D,L-penicillamine, which releases NO into the organ bath. In contrast, the aortic sensitivity to the organic nitrates pentaerythritol tetranitrate and isosorbide 5-nitrate, which release NO after enzymatic metabolization within the smooth muscle, was not reduced. CONCLUSIONS: These results suggest that the impairment of endothelium-dependent vasorelaxation induced by atherosclerosis is dependent on gender. This may be due to a greater degradation of extracellular NO in the vessel wall of males.

Pharmacokinetics and bioavailability of pentaerithrityl tetranitrate and two of its metabolites.

Two preparations containing 100 mg pentaerithyrityl tetranitrate (PETN, CAS 78-11-5) each were administered to 24 healthy male volunteers in an open randomised two-way cross-over design. The test preparation was a commercially available 50 mg tablet (Pentalong 50 mg Tabletten, 2 tablets per dose), the reference preparation was an aqueous suspension prepared immediately before application from the same 25% PETN/lactose trituration as was used for manufacturing the tablets. Blood samples were withdrawn pre-dose and at 14 time points within 24 h after dosing. The resulting plasma was analysed by a GC/MS method developed on purpose. Since in a pilot study not a single one of 120 plasma samples contained concentrations of unchanged PETN or of its metabolite pentaerithrityl trinitrate (PE-tri-N, CAS 1607-17-6) above the quantification limit of 50 pg/ml, the samples of this study were assayed for the metabolites pentaerithrityl dinitrate (PE-di-N, CAS 1607-01-8) and pentaerithrityl mononitrate (PE-mono-N, CAS 1607-00-7) only. -Mean peak levels of 17 ng/ml and 7.5 ng/ml PE-di-N were reached ca. 3 h after application of tablets or trituration. The plasma elimination half-life was 4-5 h. Average maximum PE-mono-N levels of 79 ng/ml (tablets) and 35 ng/ml (trituration) were observed at 7 h p. appl. They declined with a half-life of 10-11 h. The relative bioavailability of the tablets as determined by means of the AUC of PE-di-N is 280-290%. This high value is explained by the specific properties of drug liberation and dissolution from the preparations used.

[Long-term effect of various nitrates in ischemic heart disease and latent heart failure]. / Untersuchungen zum Langzeiteffekt verschiedener Nitrate bei ischämischer Herzkrankheit und latenter Herzinsuffizienz.

In 24 patients (pts) with proven coronary artery disease, stable angina pectoris (AP) and elevated pulmonary artery pressure (PAP) during bicycle exercise, the acute and chronic (4 and 8 months) effects of several long-acting nitrates in different dosages: 50-300 mg pentaerythrityltetranitrate (PETN) or 40-120 mg isosorbide dinitrate (ISDN) were evaluated in comparison to sublingual nitroglycerin. Nitroglycerin was about 30%-40% more effective than PETN and ISDN with regard to pulmonary artery pressure at exercise. Beneficial effects of both long-acting nitrates were shown with regard to the number of anginal attacks, nitroglycerin consumption, and ST-segment depression both during short- and long-term treatment. Both nitrates decreased exercise pulmonary artery pressure by 15%-20%, at acute testing and during chronic therapy. There was no difference with respect to the long-term effects of both long-acting nitrates. However, more side-effects were observed during ISDN treatment. There were no signs of nitrate tolerance development with the therapy schedules under investigation.

[Development and status of nitrate therapy in East Germany]. / Entwicklung und Stand der Nitrattherapie in der DDR.

Nitrates are available in the GDR as: Nitrangin liquidum (0.1 mg glycerol trinitrate/gt.) and Nitrangin isis in 0.3 and 0.8 mg capsules for preventing anginal attacks; Trinitrosan (glycerol trinitrate) for intravenous therapy of ischemic conditions and acute left heart failure; Pentalong 50 (50 mg pentaerythrityl tetranitrate, PETN) for long-term oral therapy. PETN was introduced in 1977 as Pentalong (20 mg), and in a sustained-release form as Pentalong longo (40 mg PETN/dragée: 20 mg in a coated core and 20 mg in capsule form). Patients taking Pentalong longo repeatedly reported undissolved coated pills in their feces due to the varying solubility rates of the coating. It was primarily intended that the coating ensure the sustained release of PETN from the core. Although tests confirmed that 90% of the pill did not release the PETN after 180 min in the "in vitro gastric juice" and of these 90%, another 94% had not released the PETN after 30 min in the "in vitro intestinal juice", it could not be determined what percentage of pill cores did later dissolve and release the PETN during passage through the intestines. Clinical tests on pill cores with eight coatings also revealed no predictable breakdown and release of the core contents. This was not the case with pill cores with five layers of coating, used henceforth for obtaining a sustained release effect with Pentalong longo. However, clinical examinations suggested to abandon sustained release formulations because of the high interindividual release of PETN in the gastrointestinal tract from coated dragées and the drug-inherent sustained action of PETN. The corresponding clinical experiments are the subject of this report.

A study of the plasma levels of pentaerythritol mononitrate following administration of pentaerythritol tetranitrate in combination with meprobamate and diphenhydramine.

The systemic absorption of meprobamate, diphenhydramine and pentaerythritol tetranitrate (PETN) has been demonstrated following oral administration of a formulation containing all three drug substances to human volunteers. A study undertaken in dogs has also been made of the pharmacokinetics of the major nitrated metabolite of PETN when the parent drug is administered with and without meprobamate and diphenhydramine. Pentaerythritol mononitrate shows a six-fold increase in both peak plasma concentrations and area under the 0-12 hour plasma concentration-time curve when PETN is co-administered with a combination of meprobamate, diphenhydramine and nicotinic acid. No such increase is apparent when either meprobamate or diphenhydramine is excluded from the dose. Further increases in pentaerythritol mononitrate plasma levels and AUC 0-12 h are observed when all of the drugs are administered as the formulated coated tablet (VisanoCor).

[Treatment of severe hypertension and hypertensive crises with nitrates]. / Die Behandlung schwerer arterieller Hypertonien und hypertensiver Krisen mit Nitrokörpern.

Taking into consideration the frequent combination of hypertension, ischaemic heart disease and heart insufficiency the effect of blood pressure as well as the influence of pre- and afterload gain increasing importance, when nitrates are used. It is the question, whether the blood pressure reducing effect may be used with a certain aim or not. In own investigations acute haemodynamic experiments with glycerol trinitrate were carried out on 10 patients with arterial hypertension (catheterization, estimation of HMV and so on) in rest and under ergometric load, clinical therapeutic experiments on 10 patients with crisis of hypertension with cerebral and/or cardiac complications as well as long-term experiments with pentaerythrityl tetranitrate on 6 patients with in most cases severe arterial hypertension. The acute effects on the haemodynamics correspond to those in normal blood pressure, in which case the reduction of blood pressure and resistance is more expressed. The favourable effect of glycerol trinitrate in the crisis of hypertension with cardiovascular complications can be regarded as proved. First own experiences with the long-term application of nitrates do not yet result in a clear estimation of effectivity and indications.