Effects of sulfobromophthalein and ethacrynic acid on glyceryl trinitrate relaxation.

The effects of sulfobromophthalein (SBP) and ethacrynic acid (ECA), both inhibitors of glutathione S-transferase (GST), or glyceryl trinitrate (GTN)-induced vasorelaxation were investigated in rabbit aortic strips. The aortic strips were pre-contracted with phenylephrine, followed by relaxation with 0.5 microM GTN, with or without 0.1 mM SBP or ECA. ECA was observed to inhibit GTN relaxation approximately 32%, whereas SBP did not alter the GTN activity. The dinitrate metabolites (GDN) of GTN in the tissues were also measured. The amounts of both GDNs were decreased in the ECA-treated, but not the SBP-treated group. Moreover, in the ECA-treated group, a strong correlation was obtained between the loss of GTN activity and the decrease in GTN metabolism. Concentration-response studies also revealed that ECA attenuates GTN relaxation. The slope factor of the concentration-response curves was decreased by ECA, but not by SBP, although both inhibitors caused a mild decrease in Emax. In the 9000 g supernatant of rabbit aorta, ECA was also observed to inhibit GTN metabolism more significantly than SBP. The results suggest that the mechanism of GTN activation may involve a GST isozyme that possesses high activities towards ECA.     

Efficacy of the glyceryl trinitrate transdermal therapeutic system in a dog model of heart failure.

The efficacy of a controlled-release topical dosage form of glyceryl trinitrate (Nitroglycerin Transdermal Therapeutic System, Nitroderm TTS, NTG-TTS; CAS 55-63-0) was studied in the experimental model of congestive heart failure in beagles. NTG-TTS suppressed the increase in left ventricular end-diastolic and central venous pressure, and total peripheral resistance resulting from propranolol, dextran and l-phenylephrine infusion. NTG-TTS antagonized the decrease in cardiac output in this model. These effects of NTG-TTS on congestive heart failure were presumably attributable to the reduction of pre-load, together with direct vasodilation of the peripheral arteries.     

Additive and superadditive vasodilating combinations of diltiazem and glyceryl trinitrate in isolated rabbit aorta

The combined use of two drugs with overtly similar action is a common therapeutic strategy. Combinations in doses that produce synergism are frequently sought. In this study, we examined the vasodilating action of diltiazem (DIL) and glyceryl trinitrate (GTN), tested in several fixed-ratio combinations on an isolated preparation of the rabbit aorta. This pair of drugs, widely used clinically, exhibited significant superadditivity (synergism) in certain fixed-ratio combinations tested, i.e., 30:1 and 100:1 of DIL:GTN (based on weight), and only simple additivity in other dose ratios, 1:15, 1:1, and 15:1. A demonstration of synergism requires that the total dose of the mixture needed to produce a level of effect be significantly less than the theoretically additive dose calculated; hence, statistical confidence limits of the additive value are needed. Testing of this nature has been limited for statistical reasons to drug combinations that produce parallel regressions of effect on log (dose). In this paper we illustrate the application of new statistical methodology that permits testing of drug combinations that produce nonparallel assays and report our experimental findings, which show that only certain fixed-ratio combinations of DIL and GTN are superadditive (synergistic) in this test. Although vasodilation alone does not imply antianginal action, these findings may serve as a guide for further clinical testing.     

Selective inhibition by gossypol of endothelium-dependent relaxations augments relaxations to glyceryl trinitrate in rabbit coeliac artery.

1 Acetylcholine, substance P, prostaglandin E1 and the nitrovasodilator glyceryl trinitrate induced concentration-dependent relaxations of endothelium-intact strips of rabbit coeliac artery precontracted with noradrenaline. 2 Endothelium-denuded strip preparations contracted to acetylcholine and showed no response to substance P. The relaxant response to prostaglandin E1 was unimpaired after removal of endothelium, whereas the response to glyceryl trinitrate was increased. 3 A 20 min exposure of endothelium-intact strips to gossypol, an irreversible inhibitor of the production and/or release of endothelium-derived relaxing factor, abolished vasodilatation in response to the endothelium-dependent agents acetylcholine and substance P, did not change relaxations to prostaglandin E1, but significantly enhanced relaxations in response to glyceryl trinitrate. 4 In view of the assumed common mechanism of action of endothelium-derived relaxing factor and nitrovasodilators, these results suggest an interference of the two active principles at the level of the vascular smooth muscle cell.     

Efficacy of the glyceryl trinitrate transdermal therapeutic system in a dog model of myocardial ischaemia

The efficacy of a controlled-release topical dosage form of glyceryl trinitrate (Nitroglycerin Transdermal Therapeutic System, Nitroderm TTS, NTG-TTS) was studied in the experimental model of myocardial ischaemia in beagles. At blood concentrations similar to those attained in clinical practice, NTG-TTS suppressed the ST elevation in the electrocardiogram (ECG) reflecting ischaemic change due to coronary ligation and antagonized the decrease in coronary blood flow resulting from intracoronary injection of angiotensin II (Ang II). Like those of the well-known, conventionally administered nitrates, these anti-ischaemic effects of NTG-TTS were presumably attributable to the reduction of pre-load, together with direct vasodilatation of the coronary and peripheral arteries.     

抑肽酶与氨甲环酸在体外循环中血液保护的对比研究

目的探讨抑肽酶及氨甲环酸的抗纤溶效果。方法兔体外循环,24只新西兰白兔,随机分为三组(每组8只),A:对照组,B:氨甲环酸组,C:抑肽酶组。观察体外循环2小时前后血中活化部分凝血活酶时间(APTT),凝血活酶时间(TT),纤维蛋白原(FIB)及D-二聚体(D-D)的改变。结果三组中活化部分凝血活酶时间(APTT)、凝血活酶时间(TT)及纤维蛋白原(FIB)变化相似(P>0.05)。体外循环2小时后,血液中D-二聚体(D-D)含量在抑肽酶组明显低于A、B组(P=0.019及P=0.005)。结论抑肽酶的抗纤溶作用明显优于氨甲环酸。     

Pharmacodynamic and pharmacokinetic evaluation of a new transdermal delivery system with a time-dependent release of glyceryl trinitrate.

The pharmacokinetics of glyceryl trinitrate (GTN) and its main metabolites as well as the hemodynamic effects of a new transdermal delivery system (TDS) were investigated in ten healthy male volunteers using a single blind, placebo-controlled study design with an application period of active drug of 4 successive days. The adhesive-type matrix system contains 20-mg GTN and released about 75% in a time-dependent manner. The plasma concentrations of GTN and its metabolites 1-2- and 1-3 glyceryl dinitrate reflected the time-dependent release with higher plasma concentrations during the first 12 hours than during the second 12 hours. Continuous administration of the TDS, which released 15 mg GTN/day, caused an accumulation of GTN in the plasma (about 70% greater AUC at the fourth day in comparison with the first day). The total effect per dose on the a/b-ratio of the digital pulse (height of the peak of the systolic wave divided by height of the peak of the dicrotic wave) and the reflex tachycardia were diminished by about 50% and 37%, respectively, at the fourth treatment day. The effect on systolic blood pressure measured under orthostatic conditions was blunted already 8 hours after the first application. The effect of sublingually administered GTN on digital pulse was attenuated during administration and also 1 hour after removal of the last TDS. The effect was restored 8 to 12 hours after removal of the TDS. Thus, the discontinuous release of GTN from the new system does not prevent the decline of hemodynamic efficacy during continuous therapy.     

小剂量止血环酸与抑肽酶在体外循环手术中的应用

目的 比较小剂量止血环酸与抑肽酶对体外循环术中纤溶系统、血小板及术后出血量的影响。方法 ４０例行心脏直视术患随机分为抑肽酶组（Ａ）与血环酸组（ＴＡ）,各２０例,Ａ组将３００万ＫＩＵ抑肽酶在体外循环前加入预冲液中,ＴＡ组于麻醉诱导后静注负荷量２０mg.kg^-1达１０h,并开始持续静滴２mg.kg^-1.h^-1。分别于用药前、体外循环３０min时、用鱼精蛋白后１０min、停体外循环后２h四个时点,测定血小板计数、血栓素Ｂ２（ＴＸＢ２）、血小板α膜蛋白１４０（ＧＭＰ－１４０）、纤溶酶活性（Ｐlm)、纤维蛋白降解产物（ＦＤＰ）,并记录术后１２h、２４h和总胸液引流量、术中出血量。结果 两组相比在血小板计数、纤溶酶活性、ＦＤＰ浓度及术后引流量及出血量均无显差别（Ｐ>0.05)。ＴＡ组ＣＰＢ开始后ＴＸＢ２浓度高于Ａ组（Ｐ<0.01),且ＣＰＢ后ＧＭＰ－１４０浓度恢复较Ａ组缓慢（Ｐ<0.05)。结论 小剂量持续应用止血环酸在抑制纤溶,减少心脏手术后后出血量方面与抑肽酶常规用法相比无明显差异,仅在血小板功能保护方面稍逊于后。小剂量持续应用止血环酸在抑制纤溶,减少心脏手术后出血量方面与抑肽酶常规用法相比无明显差异,仅在血小板功能保护方面稍逊于后。小剂量持续应用止血环酸安全有效、价格低廉,故可广泛应用于体外循环手术。     

Pentaerythritol trinitrate and glyceryl trinitrate on intramyocardial oxygenation and perfusion in the dog. Krogh analysis of transmural metabolism

1. The effect of intravenous pentaerythritol trinitrate and glyceryl trinitrate on left ventricular subepicardial (epi) and subendocardial (endo) Po₂ and perfusion were compared in anaesthetized open-chest mongrel dogs. Tissue Po₂ was determined simultaneously at a depth of 3 mm (epicardial) and 9 mm (endocardial) with small platinum electrodes by polarography. In a separate series of dogs tissue perfusion of those regions was measured by hydrogen (H₂) clearance using similar electrodes. 2. Both nitrates increased endocardial Po₂ while epicardial Po₂ was not altered. Perfusion was determined at the point of the maximal rise in endocardial Po₂ (4–7 min after injection of either nitrate). At that period average coronary artery inflow and epicardial perfusion were decreased but endocardial perfusion was not significantly altered. 3. Using the data on Po₂, hydrogen clearance and intercapillary distance, the effect of the nitrates on transmural metabolism (oxygen consumption) was estimated by Krogh analysis. Basal endocardial metabolism was 20–30% higher than epicardial metabolism. The nitrates reduced metabolism in each region. The absolute decrease in oxygen consumption was greater in the endocardium. 4. The results show that both pentaerythritol trinitrate and glyceryl trinitrate improve endocardial oxygenation by producing a more favourable balance between perfusion and oxygen requirements in that region.     

Impact of tranexamic acid vs. aprotinin on blood loss and transfusion requirements after cardiopulmonary bypass: a prospective, randomised, double-blind trial

INTRODUCTION: Aprotinin (AP) reduces blood loss and transfusions after cardiopulmonary bypass (CPB), but may sensitise patients and is expensive. Tranexamic acid (TA) has less side-effects, but data regarding its efficacy are controversial. The aim of our prospective, randomised, double-blind study was to compare the impact of AP vs. TA on drainage blood loss and transfusion requirements in patients undergoing first time CABG on CPB. MATERIALS AND METHODS: One hundred and twenty adult patients were randomised to receive either high-dose AP according to Hammersmith or a total of 2 g TA. Perioperative blood products were transfused in a standardised fashion. Blood loss was measured up to 24 h. Demographic and clinical patient data were collected until hospital discharge. RESULTS: The data from 118 patients (TA: n = 58, AP: n = 60) who completed the study according to protocol were analysed. Blood loss at 24 h postoperation in TA patients was significantly higher (896 +/- 354 ml) as compared to AP patients (756 +/- 347 ml; p = 0.03). TA patients received 1.5 +/- 1.5 units of red blood cells (AP: 1.5 +/- 1.7, p = 1.0), 1.3 +/- 2.0 units of fresh frozen plasma (AP: 1.0 +/- 2.0, p = 0.38) and 0.5 +/- 1.4 units of platelets (AP: 0.2 +/- 0.7, p = 0.15). Clinical data, including perioperative myocardial infarction rate, acute renal failure, mechanical ventilation, hospital stay and mortality, were not significantly different between either group. CONCLUSION: Our data show a difference in blood loss between TA and high-dose AP. Although statistically significant, it has little clinical relevance, because perioperative transfusion requirements were similar for both groups. Thus, TA appears to be a cost-effective alternative to AP in primary CABG patients.     

Impact of tranexamic acid vs. aprotinin on blood loss and transfusion requirements after cardiopulmonary bypass: a prospective,randomised, double-blind trial

Summary

Introduction: Aprotinin (AP) reduces blood loss and transfusions after cardiopulmonary bypass (CPB), but may sensitise patients and is expensive. Tranexamic acid (TA) has less side-effects, but data regarding its efficacy are controversial. The aim of our prospective, randomised, double-blind study was to compare the impact of AP vs. TA on drainage blood loss and transfusion requirements in patients undergoing first time CABG on CPB.

Materials and Methods: One hundred and twenty adult patients were randomised to receive either high-dose AP according to Hammersmith or a total of 2 g TA. Perioperative blood products were transfused in a standardised fashion. Blood loss was measured up to 24 h. Demographic and clinical patient data were collected until hospital discharge.

Results: The data from 118 patients (TA: n = 58, TA appears to be a cost-effective alternative to AP AP: n = 60) who completed the study according to protocol were analysed. Blood loss at 24 h postoperation in TA patients was significantly higher (896 ± 354 ml) as compared to AP patients (756 ± 347ml; p = 0.03). TA patients received 1.5 ± 1.5 units of red blood cells (AP: 1.5 ± 1.7, p = 1.0), 1.3 ± 2.0 units of fresh frozen plasma (AP: 1.0 ± 2.0, p = 0.38) and 0.5 ± 1.4 units of platelets (AP: 0.2 ± 0.7, p = 0.15). Clinical data, including perioperative myocardial infarction rate, acute renal failure, mechanical ventilation, hospital stay and mortality, were not significantly different between either group.

Conclusion: Our data show a difference in blood loss between TA and high-dose AP. Although statistically significant, it has little clinical relevance, because perioperative transfusion requirements were similar for both groups. Thus, TA appears to be a cost-effective alternative to AP in primary CABG patients.     

Elimination of glyceryl trinitrate: effects of sex, age, species and route of administration.

1 Orally administered glyceryl trinitrate to rats undergoes extensive first pass metabolism leading to low bioavailability. 2 Sex differences in the plasma elimination of glyceryl trinitrate were seen in the rat, the female exhibiting the longer plasma half-life. No sex differences in this respect were detected in the rabbit. 3 The plasma half-life of glyceryl trinitrate was longer and the volume of distribution larger, in older animals. 4 The plasma elimination of glyceryl trinitrate was different in various animal species. There was a good correlation between plasma half-life and animal bodyweight.     

Assessment of skin safety of a new glyceryl trinitrate transdermal patch. Animal and human studies

The experimental models and the studies in man employed to assess the skin and general safety of a newly developed glyceryl trinitrate (GTN, CAS 55-63-0) transdermal patch, hereinafter coded EPI, are described. EPI was found well tolerated by the skin after single or 28-day repeated epicutaneous application on the rabbit, devoid of phototoxicity in the mouse, devoid of skin sensitizing potential in the guinea pig and devoid of photosensitizing effects in the guinea pig. Tested were also, with negative results, the cytotoxic, hemolytic and genotoxic potential, the presence of bacterial endotoxins, the systemic and intracutaneous toxicity, and the possible conjunctival irritant effects. The application of EPI for 14 consecutive days on the thoracic skin of 28 healthy volunteers did not provoke subjective discomfort such as itching, burning or pain, or objective skin lesions. On the application site a light and transient erythema was often found demonstrating the transcutaneous absorption of the vasodilating GTN from the patch. The 14-day application was followed after two weeks by the application of a challenge EPI patch to detect a possible skin sensitization by EPI. No skin reaction was elicited, showing that also in man EPI is devoid of skin sensitizing potential. During the 14-day application of EPI several GTN commonly induced systemic adverse reactions were observed, particularly headache, confirming the systemic bioavailability of GTN from the patch. Headache rapidly disappeared after removal of the patch, in parallel with the decrease of the blood concentrations of GTN and of its active metabolites, consistently with the previous pharmacokinetic findings. This is an advantage of the administration of GTN with the transdermal patch because, in the case of unbearable headache, the patient is relieved by the simple removal of the patch.     

Selective anti-platelet aggregation synergism between a prostacyclin-mimetic, RS93427 and the nitrodilators sodium nitroprusside and glyceryl trinitrate.

1. Citrated platelet-rich plasma from human donors was used to examine turbidometrically the platelet aggregation response to collagen (2.5 micrograms ml-1) and ADP (1.6 microgram ml-1). 2. With collagen as an aggregating agent, the limited (35% maximal inhibition) inhibitory effects of glyceryl trinitrate (GTN, 0.78-50 micrograms ml-1) were markedly potentiated by threshold (3.3-10 ng ml-1) concentrations of RS93427, an orally active prostacyclin-mimetic. Almost complete inhibition of aggregation could then be produced. 3. A threshold concentration of RS93427 (3.3 ng ml-1) similarly potentiated the ability of sodium nitroprusside (NaNp, 0.78-10 micrograms ml-1) to inhibit collagen-induced platelet aggregation. There was an 8 fold reduction in the IC25 concentration of NaNp. 4. Threshold concentrations of the nitrodilators were also able to potentiate the anti-aggregatory effects of RS93427 (0.03-30 ng ml-1) on collagen-induced platelet aggregation. With threshold concentrations of either GTN (6.3-25 micrograms ml-1) or NaNp (0.3-1.3 microgram ml-1), the mean IC50 concentration of RS93427 was reduced 4 or 6 fold, respectively, while the IC25 concentration was reduced 6 or 10 fold, respectively. 5. No similar synergistic interactions were seen between RS93427 and the nitrodilators when ADP was used as an aggregating agent. 6. In spontaneously hypertensive rats, the dose-response for the hypotensive response to bolus doses of RS93427 was not altered by concomitant steady state infusion of a threshold dose (1 micrograms kg-1 min-1) of GTN. 7. Possible therapeutic implications of these findings are discussed.     

Comparative in vitro study of a series of organic nitroesters: unique biphasic concentration-effect curves for glyceryl trinitrate in isolated bovine arterial smooth muscle and lack of stereoselectivity for some glyceryl trinitrate analogues.

Four different organic nitroesters, constituting a homologous series based on unbranched polyalcohols, were compared with regard to in vitro relaxation of isolated bovine mesenteric arteries contracted with 2.5 microM phenylephrine. The organic nitroesters included ethylene glycol dinitrate (EGDN), dinitratopropane (DPN), glyceryl trinitrate (GTN), and tetranitratobutane. Glyceryl trinitrate exhibited a biphasic concentration-effect relationship, with pD2 values of 11.5 +/- 0.5 and 7.2 +/- 0.2 for the high-pD2 and low-pD2 component of the relaxation curve, respectively. The high-pD2 and low-pD2 component contributed 28 and 72% of the maximal response, respectively. EGDN, DPN, and tetranitratobutane induced monophasic concentration-effect curves with pD2 values of 7.4 +/- 0.1, 7.8 +/- 0.2, and 6.9 +/- 0.6, respectively. Stereoisomeric forms of DPN and tetranitratobutane showed no difference with regard to relaxing potency in bovine mesenteric artery. GTN has a partly unique mechanism for vascular smooth muscle relaxation that distinguishes this compound from other related organic nitroesters.     

Tissue disposition of glyceryl trinitrate, 1,2-glyceryl dinitrate, and 1,3-glyceryl dinitrate in tolerant and nontolerant rats.

The tissue distribution of glyceryl trinitrate (GTN) and its two dinitrate metabolites 1,2-glyceryl dinitrate (1,2-GDN) and 1,3-glyceryl trinitrate (1,3-GDN), was studied in GTN-tolerant and nontolerant male Sprague-Dawley rats. The concentrations of GTN, 1,2-GDN, and 1,3-GDN were measured in plasma, heart, brain, liver, aortic tissue, and adipose tissue at various time points after a subcutaneous dose of GTN (50 mg/kg). At the first time point (5 hr), concentrations of GTN, 1,2-GDN, and 1,3-GDN in plasma were equal for tolerant and nontolerant rats, but the elimination rate was altered for the tolerant rats as compared with nontolerant rats. In adipose tissue, the concentration of GTN was significantly higher as compared with concentrations of the dinitrate metabolites. In contrast, the other tissues studied showed significantly higher concentrations of the GDNs when compared with GTN. The 1,3-GDN/1,2-GDN ratio decreased with time for both tolerant and nontolerant rats. This study indicates that long-term GTN administration results not only in tolerance development, but also in altered pharmacokinetics of GTN, 1,2-GDN, and 1,3-GDN. The results also show that the 1,3-GDN/1,2-GDN ratio is dependent on the GTN concentration.     

Effects of isosorbide dinitrate spray on central hemodynamics. Comparison with sublingual glyceryl trinitrate and isosorbide dinitrate

Effects of isosorbide dinitrate (ISDN) spray (Iso Mack Spray) on central hemodynamics were determined in comparison to sublingual glyceryl trinitrate (nitroglycerin) and ISDN, paying particular attention to their onset and duration of action. In nine patients with uncomplicated acute myocardial infarction, ISDN spray (2 sprays, 2.5 mg) glyceryl trinitrate (TNG, 0.3 mg) and ordinary ISDN tablet (5 mg) were administered by the single-blind crossover method under hemodynamic monitoring with a Swan-Ganz catheter. Systolic pulmonary artery pressure (s-PA), systolic pressure (s-BP) and heart rate were measured every minute for 10 min, every 5 min for the subsequent 20 min and thereafter every 15 to 30 min up to 120 min. Using s-PA as a measure of nitrate action, the onset and duration of action as well as the magnitude of change was compared among the three drugs. ISDN spray had a quick onset of action (2.67 +/- 2.4 min, mean +/- SD) comparable to that of TNG (2.67 +/- 1.00 min), while ISDN spray had a long duration of action (57.4 +/- 42.1 min), which was comparable to that of sublingual ISDN (85.6 +/- 39.5 min, ns) and was significantly longer than that of TNG (11.4 +/- 6.4 min, p less than 0.05). ISDN spray (2.5 mg) showed the same hemodynamic changes as were induced by 0.3 mg TNG or 5 mg ISDN. The results of this study led us to conclude that ISDN spray is a useful agent which induces the abortion of anginal attacks by its quick onset and long duration of action.     

Relationship between myoglobin contents and increases in cyclic GMP produced by glyceryl trinitrate and nitric oxide in rabbit aorta,right atrium and papillary muscle

Summary Effects of glyceryl trinitrate (GTN) and nitric oxide (NO) on the cardiac functions and myocardial cyclic GMP (cGMP) contents were examined in comparison with those in the aorta and correlated with myoglobin (an inhibitor of soluble guanylate cyclase) contents using the preparations isolated from the reserpinized rabbit.GTN (10^–10-10^–4mol/l) produced a dose-dependent relaxation in the aorta. However, this compound exerted no effect on the rate of the spontaneous beat of the right atrium and the contraction of the papillary muscle. A transient and significant increase in cGMP was observed in the aorta with GTN (3 × 10^–6 mol/l). Although the increase was also observed in the right atrium, it was much smaller. No definite change was observed in papillary muscle. Increases in cGMP produced by NO (3 × 10^–6 mol/l) were larger and significant in all tissues; (AUC_cGMP(GTN)/AUC_cGMP(NO)) ratio was 30.1 for the aorta, 65.0 for the right atrium and 16.3% for the papillary muscle. Although higher concentrations of NO were necessary in the right atrium and papillary muscle to induce increases in cGMP, no differences were noted in the three tissues as regards the maximum accumulation of this substance. Furthermore, kinetic analysis of NO-induced increases in tissue cGMP indicated no marked difference in the production rate among the three tissues, while the rate of elimination of cGMP was lower in the aorta than in the atrium or the papillary muscle. The increases in cGMP observed in these three tissues were inversely related to the contents of myoglobin in respective tissues. No effect on myocardial function was observed with NO up to the concentration of 3 × 10^–5 mol/l.These results suggest that myoglobin, an endogenous inhibitor of activation of soluble guanylate cyclase by NO, was responsible for the lower production of cGMP by NO and GTN in the myocardial tissue. Correspondence to T. Ishibashi at the above address     

Endothelial nitric oxide synthase is a site of superoxide synthesis in endothelial cells treated with glyceryl trinitrate

Tolerance to glyceryl trinitrate (GTN) involves superoxide (O(2)(*-)) production by endothelial cells. Nitric oxide synthase (NOS) produces O(2)(*-) when L-arginine (L-arg) is limited. The purpose of this study was to test the hypothesis that GTN stimulates NOS to increase O(2)(*-) synthesis in endothelial cells when L-arg is limited. Production of O(2)(*-) by bovine aortic endothelial cells (BAEC, passages 3 - 5) was determined by spectrophotometrically measuring superoxide dismutase-inhibited reduction of ferricytochrome C to ferrocytochrome C. Cells were incubated in buffer without L-arg. O(2)(*-) production was measured using BAEC either untreated or treated with L-NAME or L-arg alone or following treatment with GTN (10(-9) to 10(-6) M) for 30 min or DPTA NONOate (10(-7) and 10(-6) M) alone or with GTN or DPTA NONOate after pretreatment with nitro-L-arginine methyl ester (L-NAME), L-arg or their inactive enantiomers, D-NAME or D-arg (all 5 x 10(-4) M) (n=6 - 7/group). L-NAME alone produced a 69% reduction in O(2)(*-) levels. Treatment with L-arg alone had no effect. Cells treated with GTN alone exhibited an increase in O(2)(*-). This effect was prevented by pretreatment with either L-NAME or L-arg, and was unaffected by D-NAME or D-arg. We observed a dose-response relationship in O(2)(*-) production to GTN over a range of 10(-9) to 10(-7) M. The NO donor, DPTA-NONOate, unlike GTN, did not have a significant effect on O(2)(*-) production. In conclusion, endothelial NOS is a site of O(2)(*-) synthesis in endothelial cells activated by GTN.     

Blood levels of the metabolites of glyceryl trinitrate and pentaerythritol tetranitrate after administration of a two-step preparation.

Blood levels and urinary excretion rates of glyceryl trinitrate- pentaerythritol tetranitrate, and their less nitrate containing metabolites have been determined in ten human volunteers after a single dose of a two- step preparation containing glyceryl trinitrate and pentaerythritol tetranitrate. Blood levels accounted for peak levels of about 40% of the glyceryl trinitrate and 0.4% of the pentaerythritol tetranitrate metabolites, respectively. Within the first 24 h post administration 22% of the glyceryl trinitrate and 19% of the pentaerythritol tetranitrate were excreted as nitrate metabolites, chiefly in form of conjugates. The determinations were obtained by gas chromatography on extremely inactive columns and electron capture detection by means of derivatives.