Hemolytic Potential of Structurally Related Aniline Halogenated Hydroxylamines

This study was undertaken to investigate the hemolytic potential of several structurally related aniline halogenated phenylhydroxylamines based on their decreasing electro negativity. The compounds compared are phenylhydroxylamine (PHA) and para-fluoro-, para-bromo-, and para-iodo-phenylhydroxylamines. Red blood cells of male Sprague-Dawley rats were labeled with radioactive chromium-51 and exposed to the test agent before being infused into the tail vein of isologous rats. The time course of blood radioactivity was monitored. The stability of some selected halogenated aniline analogs was also determined in blood. All four tested hydroxylamines produced dose-dependent reduction in the circulating labeled red blood cells indicating their destruction and loss. The most pronounced reduction was observed at doses from 175 to 250 microM. The dose of 100 microM appeared to be the threshold limit. The para-iodo-PHA was two times more toxic than para-fluoro-PHA in the destruction of red blood cells in rats.

Measurement of anti-cancer agent methoxyamine in plasma by tandem mass spectrometry with on-line sample extraction

In this work, we present the development and validation of a tandem mass spectrometry method for the quantitative determination of methoxyamine (CH3ONH2), a potential new chemotherapeutic agent, in human and mouse plasma. Methoxyamine together with the internal standard (I.S.) methoxyl-D3-amine was directly derivatized in plasma sample with a novel chemical agent 4-(N,N-diethylamino)benzaldehyde. The product solution was injected into an on-line Oasis HLB extraction column (2.1 mm x 20 mm) for analyte extraction. After the elution of extractives, the derivatized analytes were monitored by the positive-electrospray-ionization mass spectrometry (ESI-MS-MS). The structures of derivatized analytes were elucidated by fragmentation. Quantitation of plasma methoxyamine was carried out by the multiple reaction monitoring (MRM) mode. This method had a linear calibration range of 1.00-1000 ng/ml with a correlation coefficient of 0.9999 for methoxyamine in both human and mouse plasma. The limit of detection (LOD) and limit of quantification (LOQ) for methoxyamine in plasma were 0.150 and 0.500 ng/ml, respectively. It was demonstrated that the method had high recovery and accuracy (90.1-94.7 and 90.1-96.3%), as well as excellent intra- and inter-assay precision (2.2 and 3.7%), at three concentration levels (5.00, 50.0, 500 ng/ml). This method has been used to analyze the plasma levels of methoxyamine in samples obtained from male CD1 mice after bolus intraperitoneal injection of 2, 5 and 20mg methoxyamine hydrochloride (CH3ONH2.HCl) per kilogram mouse.

New strategy for antedrug application: development of metalloproteinase inhibitors as antipsoriatic drugs

Phosphonamide-based inhibitors were synthesized and evaluated for the inhibitory activities against the shedding of epidermal growth factors, amphiregulin and heparin-binding EGF-like growth factor, that would participate in the development of psoriasis. All compounds exhibited excellent inhibitory activities for these EGF sheddings; however, they also inhibited matrix metalloproteinases (MMPs). To avoid adverse effects reported by the clinical development of MMP inhibitors, the antedrug concept was introduced. Among the phosphonamide inhibitors, the 2,2,2-trifluoroethyl ester 8d and 2,2-difluoroethyl ester 8c showed rapid decomposition in human plasma, which is an essential property for the antedrug. Topical applications of these compounds significantly suppressed TPA-induced epidermal hyperplasia in murin skin, a model of psoriasis. These results suggested that the phosphonamide-based inhibitors have a therapeutic potential for the treatment of psoriasis as an antedrug application.

[Normal values of plasma methoxyamines in the setting of renal insufficiency and peri-operative stress. Consequences for the etiological diagnosis of hypertension]

INTRODUCTION

HPLC plasma methoxyamines measurements are the updated technique for the diagnosis of adrenergic hypersecretion. Their reliability meets that of urinary measurements. Significance of increased values is not yet fully established for the etiological diagnosis of hypertension in some situations, especially in case of renal insufficiency and in the peri-operative period. The aim of this study is to define the "normal" range of the values of plasma methoxyamines in both of those conditions.

PATIENTS AND METHODS

in a General and Endocrine Surgical Unit, 3 homogeneous group of 20 patients each have been studied: group 1, control (patients awaiting thyroidectomy); group 2, patients on maintenance hemodialysis submitted for hyperparathyroidism; group 3, patients submitted to digestive surgery. Measurements were done pre-operatively in group 1, pre and post-operatively in group 2, and post-operatively in group 3.

RESULTS

in comparison to the control (11.8 nmol/l), we observed in group 2 a 18 fold increase preoperatively, and a 29 fold increase at post-operative day 1. In group 3, we observed a 2.3, 2.7 and 2 fold increase at post-operative days 1,2 and 3 respectively. All those results were statistically significant.

CONCLUSION

Results of measurements of plama methoxyamines should always be matched to the serum creatinine levels. They are meaningful for the diagnosis of endocrine origin of hypertension only late after the early post-operative period.

Evaluation of the hydroxylamine Tempol-H as an in vivo radioprotector

Nitroxides are stable free radical compounds that protect against the toxicity of reactive oxygen species in vitro and in vivo. Tempol (Aldrich, Milwaukee, WI, USA) is a cell-permeable hydrophilic nitroxide and has been shown to be an in vitro and in vivo radioprotector. The limitations of Tempol as a systemic radioprotector are that it causes substantial reductions in arterial blood pressure when administered intravenously and is associated with seizure activity. Furthermore, Tempol is rapidly reduced to its hydroxylamine form, Tempol-H, which limits the period of time the active form of the nitroxide is available for radioprotection. Based on initial pharmacological and blood pressure experiments performed in mice, we hypothesized that the systemic administration of Tempol-H in vivo would lead to an equilibration between Tempol and Tempol-H that would limit the toxicity of the nitroxide and provide in vivo radioprotection. Tempol-H was administered in increasing doses via an intraperitoneal route to C3H mice. The maximally tolerated dose was found to be 325 mg/kg. The whole-blood pharmacology of Tempol-H was investigated with electron paramagnetic resonance spectroscopy. These studies demonstrated the appearance of Tempol in whole blood immediately after intraperitoneal injection, suggesting that rapid oxidation of Tempol-H to Tempol takes place in vivo. Although the peak concentration of Tempol in whole blood after administration of Tempol-H did not reach the same levels as those observed when Tempol is administered, the whole-blood levels of Tempol were similar by 10 min after injection. Tempol-H provided protection against the lethality of whole-body radiation in C3H mice at 30 d with a dose modification factor of 1.3, which is similar to the results obtained with Tempol. Hemodynamic measurements in C3H mice after intravenous injection showed that Tempol-H produced little effect on blood pressure or pulse compared with Tempol. Tempol-H is a systemic in vivo radioprotector of C3H mice and is associated with less hemodynamic toxicity than Tempol.

[The biological diagnosis of pheochromocytoma]

Pheochromocytomas are tumors secreting large amount of catecholamines. Elevation of blood pressure is the classical manifestation but frequently the tumors are silent and they have to be screened systematically. The biological diagnosis is essential to affirm the tumor before any imaging procedure. It needs to select the most sensitive and specific methods. The sensitivity of VMA, urinary catecholamines and plasma catecholamines assays is respectively 70%, 75%, 85%. Determination of methoxyamines in the urine or better in the plasma reaches a sensitivities of 98%. This represents the best tool for the diagnosis of pheochromocytomas. Only renal or heart failure decrease the specificity of the plasma methoxyamines assay.

Humoral and haemodynamic effects of idrapril calcium, the prototype of a new class of ACE-inhibitors, in essential hypertensive patients

Idrapril is the prototype of a new class of ACE inhibitors, characterised by the presence of a hydroxdmic group. Six untreated in-patients with essential hypertension were given single oral doses of the calcium salt of idrapril, idrapril calcium (200 mg) and placebo according to a double blind, randomised experimental design. Supine and upright blood pressure, heart rate, plasma idrapril serum UCE, active renin and angiotensin II were measured at timed intervals for 24 hours after dosing. Plasma idrapril reached a peak after 2 hours (3.01 microgm x ml(-1)), and by 12 hours the compound had almost disappeared (67 ng x ml(-1)). Derived t1/2 was 1.4-2.2 h. ACE activity was suppressed [from 77.9 to 3.3 after 2 hours and 11.8 after 12 hours nmol(-1) x min(-1) x ml] and angiotensin II production inhibited [from 8.8 to 3.1 (after 1 hour) and 7.5 (after 24 hours) pg x ml(-1)]. Compared to placebo, idrapril calcium significantly lowered both supine blood pressure starting at 4 hours (idrapril calcium 140/93 mmHg; placebo 157/101 mmHg; placebo 147/100 mmHg), and upright blood pressure starting at 3 hours (idrapril calcium 135/95 mmHg; placebo 147/100 mmHg) up to 24 hours (idrapril calcium 132/92 mmHg; placebo 145/100 mmHg). Idrapril calcium appears to be an effective ACE inhibitor in essential hypertension, with a hypotensive action for up to 24 h.

Pharmacokinetics and biochemical efficacy of idrapril calcium, a novel ACE inhibitor, after multiple oral administration in humans

The pharmacokinetic profile and biochemical efficacy of idrapril calcium, a novel angiotensin converting enzyme (ACE) inhibitor, were evaluated in healthy volunteers after multiple dosing for 5 days at the doses of 100, 200 and 400 mg twice daily. The study was conducted as a double-blind, cross-over comparison of idrapril calcium against placebo. Plasma concentrations of idrapril were determined by an indirect enzymatic method. Urinary concentrations were measured by reverse phase high performance liquid chromatography (h.p.l.c.). Plasma samples were also analysed for ACE activity. The pharmacokinetics of idrapril calcium did not change significantly between day 1 and day 5. The values of Cmax and AUC were dose-related over the range of doses tested; tmax was 3-4 h and apparent elimination half-life was 1.4-1.6 h. Plasma ACE activity was maximally inhibited (94-96%) at all dose levels and remained more than 80% depressed from 2 to at least 6 h after idrapril calcium. Although the maximum effect was not dose-related, the duration of inhibition showed some dose-dependency, ACE activity returning to 56, 45 and 29% of the basal value 12 h after the 100, 200 and 400 mg doses, respectively. There were no clinically significant adverse events experienced by the volunteers. No dose-related effects on blood pressure or heart rate were observed. There were no changes in clinical pathology tests, urine analyses or electrocardiograms after dosing with idrapril calcium. Idrapril calcium, the prototype of a new class of ACE inhibitors, appears to be well-tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of idrapril in rats, dogs, and humans

Idrapril is the prototype of a new class of angiotensin converting enzyme (ACE) inhibitors. Its pharmacokinetics and pharmacodynamics (plasma ACE activity) were investigated in rats, dogs (after intravenous and oral doses), and human volunteers (after oral doses). Following intravenous administration (1 mg/kg) to rats and dogs, elimination half-lives were 96 and 52 min, systemic clearance 19.6 and 9.5 ml/min kg, and volume of distribution 2.7 and 0.8 liters/kg, respectively. Pharmacokinetics appeared linear in dogs, within the dose range of 0.1-10 mg/kg. After oral administration of similar doses (approximately 2 mg/kg) in the three species studied, peak plasma concentrations were 182, 567, and 726 ng/ml; AUCs 25, 85, and 182 micrograms min/ml; and elimination half-lives 82, 54, and 174 min in rats, dogs, and healthy volunteers, respectively. Absolute oral bioavailability was calculated to be approximately 24% in rats and dogs. Idrapril did not bind to plasma proteins of the species studied. Plasma ACE was fully inhibited following oral administration of approximately 2 mg/kg in rats and humans, but in dogs maximal inhibition did not exceed 85%. Duration of action, measured as time for ACE to recover to 70% of initial activity, was approximately 5, 3, and 22 hr in rats, dogs, and humans, respectively. Idrapril plasma levels appeared correlated in a saturable way with inhibition of plasma ACE in all three species, yielding ex vivo IC50 values of approximately 7 ng/ml for both the rat and humans, and 91 ng/ml for dogs.

Acute neurotoxicity of sodium azide and nitric oxide

Sodium azide is a chemical of rapidly growing commercial importance with a high acute toxicity and an unknown mechanism of action. Although it has some chemical properties and biological effects in common with cyanide, its lethality does not appear to be due to inhibition of cytochrome oxidase. Unlike cyanide it is a potent vasodilator and inhibitor of platelet aggregation presumably by virtue of its conversion to nitric oxide in vivo and in isolated preparations of blood vessels and thrombocytes. It is not clear whether the high toxicity of azide is due to nitric oxide or to the parent anion. Of a number of possible azide antagonists tested in intact mice only phenobarbital in both anesthetic and subanesthetic doses afforded statistically significant protection against death. Diazepam, phenytoin, and an anesthetic dose of a ketamine/xylazine combination had no effect. Major motor seizures are sometimes seen in human azide poisoning, and these are a regular feature of azide poisoning in laboratory rodents. Solutions of nitric oxide given systemically to mice produced no signs of toxicity, but doses 1,000-fold lower placed in the cerebroventricular system of rats produced brief but violent tonic convulsive episodes. A dose of 0.61 mmol/kg azide as given systemically regularly produced convulsions whereas a dose of 6 mumol/kg given icv produced seizures in rats. The icv convulsive dose of azide was 50-fold larger than the icv dose of nitric oxide. These results suggest that azide lethality is due to enhanced excitatory transmission in the central nervous system perhaps after its conversion to nitric oxide.(ABSTRACT TRUNCATED AT 250 WORDS)

A rare fatal case of silicone resin precursor (SH792) poisoning

A 39-year-old man committed suicide by ingesting a large quantity of SH792. SH792 is a silicone resin precursor used as a hardener for waterproof paints. It is polymerized in water; this process is then followed by the formation of silicone resin and the release of N,N-diethylhydroxylamine. In this decedent, analysis by infrared spectroscopy showed that polymerized silicone resin was present in the stomach contents. The amount of silica in his tissues was within levels seen in control subjects. N,N-diethylhydroxylamine was detected in the urine (0.7 microliters/ml) but not in the stomach contents. The data suggest that SH792 was polymerized in the stomach and the released N,N-diethylhydroxylamine (DEHA) was absorbed into the body. The mechanism of SH792 poisoning is also discussed.

Aniline-, phenylhydroxylamine-, nitrosobenzene-, and nitrobenzene-induced hemoglobin thiyl free radical formation in vivo and in vitro

We have employed the ESR spin trapping technique in vivo to detect the formation of the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)/hemoglobin thiyl free radical adduct in the blood of rats following administration of either aniline, phenylhydroxylamine, nitrosobenzene, or nitrobenzene. This DMPO adduct was a six-line, strongly immobilized, radical adduct. Using rat red blood cells, both phenylhydroxylamine and nitrosobenzene were able to induce the formation of the DMPO/glutathiyl free radical adduct and the same DMPO/hemoglobin thiyl free radical adduct was detected in in vivo samples. In experiments using purified rat oxyhemoglobin, a four-line, weakly immobilized, DMPO/hemoglobin thiyl free radical adduct was detected, in addition to the six-line strongly immobilized adduct. When this study was repeated using human red blood cells, we detected only the DMPO/glutathiyl free radical adduct and, when purified human oxyhemoglobin was employed, only the four-line, weakly immobilized, DMPO/hemoglobin thiyl radical adduct could be detected. In a study using reduced glutathione, we found that phenylhydronitroxide free radicals were reduced by glutathione and that glutathione was concomitantly oxidized to its thiyl free radical. We propose that the species responsible for the oxidation of the thiols to yield the thiyl free radicals in vivo and in vitro was the phenylhydronitroxide radical produced from the reaction of phenylhydroxylamine with oxyhemoglobin.

Detoxication of N-oxygenated arylamines in erythrocytes. An overview

1. Reactive N-oxygenated arylamines, namely, N-hydroxyarylamines and nitrosoarenes, are toxic, mutagenic, carcinogenic and allergenic. 2. Erythrocytes are a very sensitive target for these compounds, but little is known of the detoxication capacity of these cells. 3. This overview considers the most important reactions of p-substituted N-oxygenated arylamines in red cells, namely, (i) ferrihaemoglobin formation by N-hydroxyarylamines with concomitant co-oxidation to nitrosoarenes; (ii) compartmentation of nitrosobenzenes by ligation to deoxyhaemoglobin, (iii) reactions of nitrosobenzene with glutathione, (iv) adduct formation of nitrosobenzenes with thiol groups of haemoglobin. 4. To predict the metabolic fate of N-oxygenated arylamines in red cells, the respective kinetic parameters of reactions (i) to (iv) have been determined, and indicate good linear free energy correlations (pH 7.4, 37 degrees C). These data may help to estimate the detoxication capacity of erythrocytes in vivo.

Metabolism of dapsone to a hydroxylamine by human neutrophils and mononuclear cells

Dapsone is an effective anti-inflammatory agent in conditions in which inflammation is mediated by neutrophils. Dapsone also has been associated with agranulocytosis. We found that neutrophils, which had been activated by a phorbol ester or opsonized zymosan, oxidized dapsone to its nitroderivative. It appears as if this is due to oxidation of dapsone by myeloperoxidase to the hydroxylamine, followed by nonenzymatic oxidation of the hydroxylamine to the nitroderivative. The hydroxylamine can be isolated if ascorbic acid is added to the incubations. Monocytes also contain myeloperoxidase and activated mononuclear leukocytes also metabolize dapsone to the hydroxylamine. Dapsone also causes a mononucleosis-like syndrome. The reactive hydroxylamine could be responsible for both the pharmacologic and toxic properties of dapsone.

Role of dapsone hydroxylamine in dapsone-induced hemolytic anemia

The hemolytic anemia which frequently accompanies treatment of individuals with dapsone and other arylamine drugs is believed to be caused not by the parent drugs per se, but rather by metabolites which are formed during the clearance of the drugs in vivo. To determine whether the N-hydroxyarylamine metabolites of dapsone could be responsible for dapsone-induced hemolysis, dapsone, dapsone hydroxylamine (DDS-NOH) and monoacetyldapsone hydroxylamine were administered to rats which had previously received 51Cr-labeled red blood cells. All three compounds caused an increase in the rate of disappearance of radioactivity from the blood as compared with saline-treated controls. In parallel in vitro studies, incubation of 51Cr-labeled red blood cells with DDS-NOH, but not dapsone or monoacetyldapsone, induced a decrease in survival time of the radiolabeled cells when they were reintroduced into isologous rats. The disappearance of radioactivity from the blood was matched by its selective uptake into the spleen. The amount of damage (as measured by decreased red cell survival in vivo) was proportional to both concentration and time of exposure to DDS-NOH. The area under the blood concentration vs. time curve for total arylhydroxylamines (DDS-NOH + monacetyldapsone hydroxylamine) in rats given a hemotoxic dose of dapsone was similar to that of rats given an equitoxic dose of DDS-NOH. Collectively, these data indicate that the hydroxylamine metabolites of dapsone are direct acting hemolytic agents that are formed from dapsone in sufficient amounts to account for their being the sole mediators of dapsone-induced hemolytic anemia in the rat.

Contribution of aniline metabolites to aniline-induced methemoglobinemia

Methemoglobinemia after aniline and certain aniline derivatives is thought to be mediated by toxic metabolites formed during the hepatic clearance of the parent compounds. However, three aniline metabolites--phenylhydroxylamine, 2-aminophenol, and 4-aminophenol--catalyze methemoglobin formation in erythrocyte suspensions and, hence, could contribute to methemoglobin formation in vivo after aniline. To determine the relative contributions of these aniline metabolites to aniline-induced methemoglobinemia in rats, we determined time courses of methemoglobinemia in rat erythrocyte suspensions and in rats after treatment with 2- and 4-aminophenol, phenylhydroxylamine, and aniline. The relative potencies for methemoglobin production in vitro after phenylhydroxylamine, 2-aminophenol, and 4-aminophenol were about 10:5:1, based on both peak and area of the methemoglobin versus time curve. Approximate minimum concentrations for observable methemoglobin formation in vitro from these compounds were 20, 50, and 200 microM, respectively. Compared with the in vitro data, the relative potencies of the aminophenols for methemoglobinemia in rats after intraperitoneal injections were reduced with respect to phenylhydroxylamine (to 100:4:1, respectively), apparently as a result of rapid in vivo clearance of the aminophenols. Subsequent experiments, in which the time courses of the aniline metabolites were determined in blood after toxic doses of aniline, demonstrated that only phenylhydroxylamine (measured as phenylhydroxylamine + nitrosobenzene) accumulated to blood levels exceeding the minimum concentration required for methemoglobin production in vitro. In addition, blood levels of phenylhydroxylamine remained in the toxic range throughout most of the methemoglobinemic response after aniline treatment. These data are consistent with phenylhydroxylamine being the sole mediator of aniline-induced methemoglobinemia in these rats.

Biologic activity of hydroxylamine: a review

Although hydroxylamine, as such, is a product of normal cellular metabolism it is also a potent mutagen in vitro. However, in spite of this potential, it has not been shown to possess carcinogenic capabilities. Indeed, this chemical has demonstrated carcinostatic activity against certain tumors in animals. In addition, hydroxylamine has been shown to inactivate or inhibit a number of cellular enzymes and some viruses in vitro. It is also a skin irritant and sensitizer. It causes dermatitis and it is corrosive to the eyes. Acute and chronic exposures to hydroxylamine have caused methemoglobinemia and sulfhemoglobinemia.

Rapid and sensitive method for the microassay of nitrosobenzene plus phenylhydroxylamine in blood

An assay method has been developed for the determination of the combined concentration of nitrosobenzene plus phenylhydroxylamine (as nitrosobenzene) in small volumes of blood. The initial step in the procedure consisted of the simultaneous oxidation of phenylhydroxylamine to nitrosobenzene and of ferrous hemoglobin to methemoglobin by ferricyanide. Nitrosobenzene in the ferricyanide-treated blood samples was then extracted into ethyl acetate, and separated and quantitated by reversed-phase high-performance liquid chromatography with electrochemical detection. The sensitivity limit for nitrosobenzene in blood was in the pmol/ml concentration range, less than 100 microliter of blood was required for assay, and the procedure was convenient for routine multisample use. In comparison with previous assays, this method was more sensitive, had a lower coefficient of variation, and required 25-40 fold smaller blood sample volumes. The method was combined with the orbital sinus bleeding technique in order to follow the nitrosobenzene time course in vivo using small serial blood samples from rats treated with intraperitoneal injections of phenylhydroxylamine or aniline.

Effects of phenylhydroxylamine and aminophenols in Japanese quail in vivo

1. The effects of phenylhydroxylamine, and o- and p-aminophenol were studied in the Japanese quail. 2. Symptoms normally observed in aniline-treated birds were seen in quail after phenylhydroxylamine dosage at > 10 mg/kg. Aminophenols (up to 50 mg/kg) did not give these symptoms. 3. Injection of phenylhydroxylamine (50 mg/kg) resulted in formation of 70% ferrihaemoglobin after 5 min, following which a rapid reduction of ferrihaemoglobin was observed. 4. Phenylhydroxylamine reached highest blood concn. of 0.2 mumol/ml after 5 min. Phenylhydroxylamine was reduced to aniline within 5 min. 5. The effects of aniline in vivo are most probably due to O2 shortage caused by ferrihaemoglobin formation.

The fate of phenylhydroxylamine in human red cells

Phenylhydroxylamine added to human red cells under aerobic conditions and in the presence of glucose was partly reduced to aniline. About half the hydroxylamine was recovered as amine after a 2-hr incubation. The aniline, after acetylation, was identified as acetanilide by melting point, Rf-value in TCL as well as UV, IR, and NMR spectroscopy. The fate of the remaining phenylhydroxylamine was followed by use of 14C-labeled phenylhydroxylamine. About 30% of the total radioactivity was bound to hemoglobin or other proteins and about 20% was found in highly polar low-molecular substances which were insoluble in organic solvents. The elucidation of the sites at which phenylhydroxylamine was bound to hemoglobin was complicated by the lability of the bonds. When purified human hemoglobin had reacted with radioactive phenylhydroxylamine, large proportions of the radioactivity bound to hemoglobin were removed by treatment with acid or with PMB for separation of alpha- and beta-chains. The radioactive compound liberated from hemoglobin by acid was found to be aniline. After reaction with phenylhydroxylamine the number of SH groups titrable with PMB was found to be diminished. Pretreatment of hemoglobin with N-ethylmaleimide or PMB decreased the amount of phenylhydroxylamine bound to hemoglobin but did not fully prevent the reaction. Tryptic digestion of hemoglobin after reaction with radioactive phenylhydroxylamine yielded tryptic peptides with lower specific activity than that of hemoglobin. Chymotryptic digestion of the tryptic core yielded a core with specific activity much higher than that of hemoglobin. Fingerprinting of the tryptic or chymotryptic hydrolyzates showed the presence of peptides with high and other ones with low or no radioactivity and of radioactive compounds which did not react with ninhydrin. In the covalent binding of phenylhydroxylamine to globin the SH group beta93 plays an important role, but other yet unknown sites are also reactive.

Hemolysis induced by 6-N-hydroxylaminopurine riboside, an adenosine analogue

6-N-Hydroxylaminopurine riboside (HAPR) was studied in man because of its therapeutic activity in several transplanted animal neoplasms. It was not cross-resistant to other antimetabolites useful in the treatment of human neoplasia. HAPR produced marked hemolytic anemia at doses far below those that might have produced any cytotoxic or therapeutic effect. There was evidence of hemolysis at total doses as low as 0.5 mg/kg given intravenously. For man, HAPR is one of the most active hemolytic drugs.