Carcinogenesis in F344 rats by N-nitrosomethyl-n-propylamine derivatives.

The carcinogenicity of N-nitrosomethyl-n-propylamine and five of its derivatives, including N-nitrosomethyl-n-butylamine, was compared by oral administration of the compounds to inbred F344 rats. N-Nitromethyl-n-propylamine and N-nitrosomethyl-n-butylamine given in drinking water induced tumors of the upper gastrointestinal tract, mainly carcinomas of the esophagus, and appeared to be of comparable potency. N-Nitrosomethyl(2-hydroxypropyl)amine also mainly induced esophageal carcinomas (100% incidence) and lung tumors, whereas N-nitrosomethyl(2,3-dihydroxypropyl)amine mainly induced nasal cavity tumors and gave rise to a high incidence of esophageal tumors; however, it appeared to be less potent than the monohydroxy compound. N-Nitrosomethyl(2-oxopropyl)amine, the ketone corresponding to N-nitrosomethyl(2-hydroxypropyl)amine, was a more potent carcinogen than the latter at comparable doses in drinking water and gave rise to a high incidence of esophageal tumors and tumors of the trachea; female rats had a high incidence (15/20) of angiosarcomas of the liver, but only 2 male rats died with this tumor. When N-nitrosomethyl(2-oxopropyl)amine was administered at a lower dose in drinking water or at the same dose given by gavage, the incidence of esophageal tumors was lower and there were fewer carcinomas. After administration of large doses in drinking water to male and female rats, N-nitrosomethyl(3-carboxypropyl)amine, a urinary metabolite of several N-nitrosomethyl-n-alkylamines that induce tumors of the urinary bladder in rats, gave rise to a high incidence of transitional cell carcinomas of the bladder. The time to death of animals with these tumors was long, and there were few other tumors.

Comparison of the carcinogenic effectiveness of N-nitrosobis(2-hydroxypropyl)amine, N-nitrosobis(2-oxopropyl)amine, N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine, and N-nitroso-2,6-dimethylmorpholine in Syrian hamsters.

For examination of metabolic interrelationships in carcinogenesis between N-nitroso-2,6-dimethylmorpholine, N-nitrosobis(2-oxopropyl)amine (CAS: 60599-38-4), N-nitrosobis(2-hydroxypropyl)amine (CAS: 53609-64-6), and N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine, each was given to a separate group of 20 female Syrian golden hamsters by gavage. All four compounds induced tumors of the pancreatic duct and lung tumors, but the incidences varied from one compound to another. In addition, N-nitrosobis(2-oxopropyl)amine and N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine induced many hepatocellular and cholangiocellular neoplasms, which the other two compounds did not. On the basis of short time to death with tumors and the relatively low total dose administered, N-nitrosobis(2-oxopropyl) amine appeared to be the most potent carcinogen in the hamster among the four. N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine was next in potency but was considerably weaker than N-nitrosobis(2-oxopropyl)amine. N-Nitroso-2,6-dimethylmorpholine, which was similar in potency to N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine, however, did not induce a significant incidence of liver tumors of any type; and N-nitrosobis(2-hydroxypropyl) amine was considerably less potent than the other three compounds. These results did not support the opinion of N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine as the proximate carcinogenic metabolite of all three compounds in the Syrian hamster but instead suggested that these compounds might have acted through formation of different and yet unknown carcinogenic intermediates.

Esophageal carcinogenesis in F344 rats by nitrosomethylethylamines substituted in the ethyl group.

The carcinogenic activity in male F344 rats of five nitrosomethylalkylamines related to nitrosomethylethylamine has been examined. All rats were tested by administration of controlled doses of the compounds in the drinking water. Nitrosomethylbenzylamine was the most potent carcinogen of the five, causing death of most animals with tumors of the upper gastrointestinal tract (mainly the esophagus) within 6 months after a total dose of 0.2 mmol. The remaining compounds, all of which can be considered true derivatives of nitrosomethylethylamine, were less potent than nitrosomethylbenzylamine but also induced a high incidence of tumors of the esophagus. Nitrosomethyl-2-phenylethylamine and nitrosomethylneopentylamine were of comparable potency, while nitrosomethyltrifluoroethylamine was considerably less potent, as measured by the time to death with esophageal tumors. Deuterium-labeled nitrosomethylethylamine, in which deuterium replaces hydrogen on the beta-carbon atom of nitrosomethylethylamine, induced a high incidence of esophageal tumors as well as liver tumors after administration of identical doses. Reactions on the beta-carbon atom of nitrosomethylethylamine might be important as well as oxidation at the alpha-carbon atoms in determining carcinogenic effects.

Induction of carcinogenesis in Fischer rats by methylalkylnitrosamines.

Five nitrosomethyl-n-alkylamines with long aliphatic chains were administered to male F344 rats by gavage for 30 weeks. The rats treated with nitrosomethyl-n-octylamine and nitrosomethyl-n-nonylamine died within one year, while a majority of those given nitrosomethyl-n-decylamine, nitrosomethyl-n-dodecylamine, and nitrosomethyl-n-tetradecylamine lived for more than 80 weeks. Apart from the spontaneous tumors found in untreated rats of this strain, the rats treated with all four compounds containing an even number of carbon atoms in the long chain developed a high incidence of transitional cell carcinoma of the bladder. In addition, the rats treated with nitrosomethyloctylamine developed tumors of the liver (hepatocellular carcinomas and some angiosarcomas), lung, and nasal cavity. Nitrosomethylnonylamine failed to induce tumors in the bladder but induced tumors of the liver (hepatocellular carcinomas and cholangiocarcinomas), lung tumors, and some tumors of the nasal cavity.

Organ-specific carcinogenesis in rats by methyl- and ethylazoxyalkanes.

Azoxyalkanes are isomeric with nitrosodialkylamines and could be similar in their biochemical and biological actions. To compare the structure-activity relations in the two series, the tumorigenic activities of four azoxyalkanes, azoxymethane, azoxyethane, Z-ethyl-O,N,N-azoxymethane, and Z-methyl-O,N,N-azoxyethane, were compared in male F344 rats by p.o. administration of 0.54 mM and 0.135 mM solutions in drinking water. In most cases, treatment lasted 30 weeks, but at the higher dose of the two ethylazoxy compounds, 24 weeks of treatment were sufficient. Most of the animals died with tumors that could be attributed to the treatments. The two ethylazoxy compounds caused much earlier death from tumors than the corresponding methylazoxy compounds. All four compounds induced a high incidence of liver neoplasms, which were mainly hepatocellular; the two ethylazoxy compounds also induced a large number of hemangiosarcomas in the liver. At both dose levels, azoxyethane induced tumors of the esophagus and nasal cavity, tumors that were not seen in any other group. Other tumors appearing in significant incidence were in the colon and ileum, induced by azoxymethane and Z-ethyl-O,N,N-azoxymethane, and kidney tumors induced by azoxymethane and Z-methyl-O,N,N-azoxyethane. In F344 rats, azoxyethane was similar in carcinogenic activity to its isomer nitrosodiethylamine, whereas azoxymethane was much less potent than nitrosodimethylamine and induced quite different tumors. These results suggest that the biochemical activation of azoxylkanes is different from the analogous nitrosodialkylamines.

Metabolism of the Z and E isomers of N-nitroso-N-methyl-(2-oxopropyl)amine by rat hepatocytes.

The metabolism of N-nitroso-N-methyl-N-(2-oxopropyl)amine was examined using freshly isolated hepatocytes from Fischer 344 rats. As determined by high performance liquid chromatography, it was found that the E isomer was preferentially metabolized when the parent mixture was used. When the two isomers were studied separately, the E isomer was efficiently metabolized in the hepatocytic system, whereas the Z isomer was not. The kinetics of disappearance of the Z isomer during metabolism was identical to that for the reequilibration of the Z isomer to the mixture of isomers in the absence of a metabolizing system.

Mutagenicity of potassium alkanediazotates and their use as model compounds for activated nitrosamines.

The mutagenicity of a series of potassium alkanediazotates in the Ames assay was studied. These compounds were isolated as solids and are soluble in dimethyl sulfoxide. Upon addition to water, they form diazohydroxides (which are postulated intermediates in the decomposition of alpha-hydroxylated nitrosamines). The diazohydroxides decompose to electrophilic intermediates which may react with macromolecules or water. In the Ames assay, potassium diazotates produced his+ revertants in Salmonella typhimurium strains TA 100 and TA 1535 but not in strains TA 98, TA 1537, or TA 1538. Methane, methane-d3, ethane, propane, and phenylmethanediazotates were mutagenic in strain TA 100, and all diazotates with the exception of phenylmethanediazotate, produced revertants in TA 1535. The order of mutagenic potency of these compounds was: methane approximately equal to methane-d3 greater than ethane, greater than phenylmethane (TA 100) greater than propane greater than phenylmethane (TA 1535) = 0. All diazotates were direct-acting mutagens and produced revertants even when no liver 9000 X g supernatant (S9) fractions were present. S9 fractions inhibited the mutagenicity of potassium diazotates, and equivalent concentrations of S9 fractions (3 mg protein per plate) from either rat or hamster liver, whether induced or not, were equally effective. Bovine serum albumin was not as effective as S9 fractions in inhibiting diazotate mutagenesis, but heat-inactivated (70 degrees for 20 min) S9 fractions were as inhibitory of methanediazotate mutagenicity as native S9 fractions were at low protein concentrations. The half-lives of mutagenicity of methane- and ethanediazotates in aqueous solutions were identical (less than or equal to 15 sec); after less than 2 min in solution, these diazotates were rendered completely inactive. The implications of these studies for mechanisms of nitrosamine action and the use of potassium alkanediazotates as model compounds for activated nitrosamines are discussed.

Carcinogenicity of 3-chloronitrosopiperidine, 4-chloronitrosopiperidine, and 3,4-dichloronitrosopiperidine in Fischer rats.

Three chlorinated nitrosopiperidines, 3-chloro-, 4-chloro-, and 3,4-dichloronitrosopiperidine, were administered to groups of 20 male Fischer 344 rats at a concentration of 0.17 mM in drinking water. Treatment with the monochloro compounds lasted for 30 weeks, while treatment with the dichloro compound lasted for 21 weeks. Almost all of the animals died with esophageal tumors. There was also a significant incidence of tumors of the forestomach and tongue in the rats treated with the monochloro compounds. Using the rate of death of the animals with tumors as an index, the relative potency of the three compounds increases from 3-chloro- to 4-chloro- to 3,4-dichloronitrosopiperidine.

Relationship between carcinogenicity and in vitro metabolism of nitrosomethylethylamine, nitrosomethyl-N-butylamine, and nitrosomethyl-(2-phenylethyl)amine labeled with deuterium in the methyl and alpha-methylene positions.

With the use of rat liver preparations, the in vitro microsomal metabolism of methylethylnitrosamine, methyl-n-butylnitrosamine, and methyl(2-phenylethyl)nitrosamine labeled with deuterium in the methyl and alpha-methylene positions has been compared with that of the parent (unlabeled) compounds. All three forms of the liver carcinogen methylethylnitrosamine are metabolized with two sets of kinetic constants. Examination of these kinetic constants suggests that both methylation and ethylation of cellular nucleophiles might be important in the carcinogenic action of these nitrosamines. The esophageal carcinogen, methyl(2-phenylethyl)nitrosamine, gave only one set of kinetic constants during metabolism. The metabolism of the three methylbutylnitrosamines gave results similar to that of the three methylethyl nitrosamines. Except for metabolism of d2-methylbutylnitrosamine to butyraldehyde, two sets of kinetic constants were found. Approximately equivalent amounts of methylating species were produced from d3-methylbutylnitrosamine and d0-methylbutylnitrosamine.

Metabolism of the liver carcinogen N-nitrosopyrrolidine by rat liver microsomes.

This report represents a study of the total metabolism of the hepatocellular carcinogen, N-nitrosopyrrolidine (NO-PYR), by rat liver microsomes and postmicrosomal supernatant. [2,5-14C]NO-PYR, which is totally extractable from aqueous solution with methylene chloride, is converted to radioactive nonmethylene chloride-extractable products by these fractions. The initial rate of conversion to nonmethylene chloride-extractable products follows simple Michaelis-Menten kinetics with an apparent Km of 3.6 x 10(-4) M NO-PYR. The major products of NO-PYR metabolism by rat liver microsomes and postmicrosomal supernatant have been isolated and identified. One product of metabolism of NO-PYR is 2-hydroxytetrahydrofuran formed by alpha-hydroxylation by the microsomes. In the presence of postmicrosomal supernatant enzymes, this compound exists only as a transient intermediate which is rapidly converted to 1,4-butanediol or gamma-hydroxybutyrate. These compounds may be cycled into general cellular metabolism resulting in the production of CO2. Two minor pathways of metabolism have also been found.

Carcinogenesis by derivatives of 1-nitroso-3,5-dimethylpiperazine in rats.

Four mononitrosopiperazines were administered to groups of 20 female Fischer 344 rats to compare their effectiveness as carcinogens. The four, 1-nitroso-3,5-dimethylpiperazine, its 4-acetyl derivative, its 4-benzoyl derivative, and 1-nitroso-3,4,5-trimethylpiperazine, were given as 0.7 mM solutions in drinking water, 100 ml to each rat per week. The length of treatment varied from 26 weeks for nitrosotrimethylpiperazine to 50 weeks for 1-nitroso-3,5-dimethyl-4-benzoylpiperazine. Dimethyl- and trimethylnitrosopiperazine gave rise to virtually 100% incidence of undifferentiated lymphomas of the thymus and leukemias within 30 weeks (in contrast to the non-C-methylated analogs which are noncarcinogenic or only weakly so). Acetyldimethylnitrosopiperazine was also a potent carcinogen, all of the rats treated with it dying within 30 weeks with tumors of the esophagus. In contrast, benzoyldimethylnitrosopiperazine was weakly carcinogenic, inducing only a small number of tumors of the forestomach and reducing the normal life span of the rats very little.

Usefulness of DSM-III axis III in psychiatric inpatients: an actuarial comparison with the DSM-II period.

This study is a retrospective evaluation of the usefulness of DSM-III axis III (physical disorders) and its ability to enhance clinical case description in general psychiatric patients. The subjects of this study consisted of two samples of 75 inpatients; each was randomly selected and age-matched to represent DSM-II (1975-1979) and DSM-III (1981-1985) periods, respectively. The results indicated a substantial and statistically significant difference in the frequency of physical disorders recorded at intake before (9.3%) and after (46.7%) the implementation of DSM-III. DSM-III axis III may significantly enhance the recording of physical disorders in psychiatric inpatients.

Targeting nitric oxide (NO) delivery in vivo. Design of a liver-selective NO donor prodrug that blocks tumor necrosis factor-alpha-induced apoptosis and toxicity in the liver.

We have designed a drug that protects the liver from apoptotic cell death by organ-selective pharmacological generation of the bioregulatory agent, nitric oxide (NO). The discovery strategy involved three steps: identifying a diazeniumdiolate ion (R2N[N(O)NO]-, where R2N = pyrrolidinyl) that spontaneously decomposes to NO with a very short half-life (3 s) at physiological pH; converting this ion to a series of potential prodrug derivatives by covalent attachment of protecting groups that we postulated might be rapidly removed by enzymes prevalent in the liver; and screening the prodrug candidates in vitro and in vivo to select a lead and to confirm the desired activity. Of five cell types examined, only cultured hepatocytes metabolized O2-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO) to NO, triggering cyclic guanosine 3',5'-monophosphate (cGMP) synthesis and protecting the hepatocytes from apoptotic cell death induced by treatment with tumor necrosis factor-alpha (TNF alpha) plus actinomycin D. In vivo, V-PYRRO/NO increased liver cGMP levels while minimally affecting systemic hemodynamics, protecting rats dosed with TNF alpha plus galactosamine from apoptosis and hepatotoxicity. The results illustrate the potential utility of diazeniumdiolates for targeting NO delivery in vivo and suggest a possible therapeutic strategy for hepatic disorders such as fulminant liver failure.

Esterase-sensitive nitric oxide donors of the diazeniumdiolate family: in vitro antileukemic activity.

We have designed a novel prodrug class that is stable in neutral aqueous media but releases bioactive nitric oxide (NO) on metabolism by esterase. Diazeniumdiolates of structure R(2)N-N(O)=N-OR', in which R' = Na, were reacted with BrCH(2)OAc to convert the spontaneously NO-releasing salts 1a (R(2)N = diethylamino) and 1b (R(2)N = pyrrolidino) to prodrugs 2a (AcOM-DEA/NO) and 2b (AcOM-PYRRO/NO), respectively, where R' = CH(2)OAc. In contrast to anions 1a and 1b (half-lives in pH 7.4 phosphate at 37 degrees C of 2 min and 3 s, respectively), 2a and 2b showed only minimal decomposition after 16 h under these conditions. Very rapid hydrolysis occurred in the presence of porcine liver esterase, however, with free anion 1a being observed as an intermediate in the esterase-induced generation of NO from 2a. The potential utility of this prodrug class is illustrated with a comparison of 1 and 2 as antiproliferative agents in NO-sensitive human leukemia cell lines HL-60 and U937. While the 72-h IC(50)'s for 1a and 1b (which generate NO throughout the medium) in HL-60 cell cultures were >600 microM, those of 2a and 2b were 8.3 and 6.4 microM, respectively. This result is consistent with our hypothesis that 2 is selectively hydrolyzed to 1 and thence to NO intracellularly. For U937 cells, the 72-h IC(50) for both 2a and 2b was 53 microM. By contrast, relatively high antiproliferative IC(50)'s (>100 microM in U937 cells) were observed for analogues in which R' = CH(2)CH(2)SC(O)Me, from which acetyl and 2-mercaptoethyl groups must be successively cleaved to free the NO-releasing diazeniumdiolate function. Within 24 h at initial concentrations of 50 microM, 2a and 2b induced apoptosis in 50% and 57% of the HL-60 cells, respectively (35% and 40% of the U937 cells, respectively). The data reveal significant in vitro antileukemic activity on the part of these novel compounds. Moreover, their substantial ease-of-handling advantages over the anionic diazeniumdiolates from which they are derived suggest their use as convenient agents for probing the biological roles of NO.

Complexes of .NO with nucleophiles as agents for the controlled biological release of nitric oxide. Vasorelaxant effects.

Selected nucleophile/nitric oxide adducts [compounds which contain the anionic moiety, XN(O-)N = O] were studied for their ability to release nitric oxide spontaneously in aqueous solution and for possible vasoactivity. The diversity of structures chosen included those in which the nucleophile residue, X, was that of a secondary amine [Et2N, as in [Et2NN(N = O)O]Na, 1], a primary amine [iPrHN, as in [iPrHNN(N = O)O]Na, 2], a polyamine, spermine [as in the zwitterion H2N(CH2)3NH2+(CH2)4N[N(N = O)O-](CH2)3NH2, 3], oxide [as in Na[ON(N = O)O]Na, 4], and sulfite [as in NH4[O3SN(N = O)O]NH4, 5]. The rate constants (k) for decomposition in pH 7.4 phosphate buffer at 37 degrees C, as measured by following loss of chromophore at 230-260 nm, were as follows: 1, 5.4 x 10(-3) s-1; 2, 5.1 x 10(-3) s-1; 3, 0.30 x 10(-3) s-1; 4, 5.0 x 10(-3) s-1; and 5, 1.7 x 10(-3) s-1. The corresponding extents of nitric oxide release (ENO) were 1.5, 0.73, 1.9, 0.54, and 0.001 mol/mol of starting material consumed, respectively, as determined from the integrated chemiluminescence response. Vasodilatory activities expressed as the concentrations required to induce 50% relaxation in norepinephrine-constricted aortic rings bathed in pH 7.4 buffer at 37 degrees C (EC50) were as follows: 1, 0.19 microM; 2, 0.45 microM; 3, 6.2 microM; 4, 0.59 microM; and 5, 62 microM. Vasorelaxant potency (expressed as 1/EC50) was strongly correlated with the quantity of .NO calculated from the physicochemical data to be released in the interval required to achieve maximum relaxation at the EC50 doses (r = 0.995). This suggests that such nucleophile/.NO adducts might generally be useful as vehicles for the nonenzymatic generation of nitric oxide, in predictable amounts and at predictable rates, for biological purposes. The particular significance for possible drug design is underscored in the very favorable potency comparison between several of these agents and the established nitrovasodilators sodium nitroprusside and glyceryl trinitrate (EC50 values of 2.0 and greater than 10 microM, respectively) in parallel aortic ring tests.

Localizing antithrombotic and vasodilatory activity with a novel, ultrafast nitric oxide donor.

Reaction of nitric oxide (NO) with L-proline in methanolic sodium methoxide yields a diazeniumdiolate product, C5H7N3O4Na2.CH3OH (PROLI/NO), that can be stabilized in basic solution but that dissociates to proline (1 mol) and NO (2 mol) with a half-life of only 1.8 s at pH 7.4 and 37 degrees C. This kinetic behavior has allowed the generation of highly localized antiplatelet and vasodilatory effects. By infusing solutions containing 4 microM PROLI/NO in 0.1 M sodium hydroxide at the rate of 1 nmol.min-1 immediately upstream from a polyester vascular graft in the unheparinized baboon circulatory system, for example, platelet deposition at the normally thrombogenic graft surface was substantially reduced relative to controls receiving only 0.1 M sodium hydroxide. In a second study, infusion of PROLI/NO into the right atrium of sheep with induced pulmonary hypertension selectively dilalated the lung vasculature, dose-dependently reducing the pulmonary arterial pressure by as much as 9 mmHg with no observable effect on the systemic arterial pressure at an infusion rate of up to 24 nmol.kg-1.min-1. PROLI/NO could also be formulated as an insoluble polymer blend that released NO smoothly for prolonged periods. The results suggest that localized delivery of diazeniumdiolates such as PROLI/NO which generate NO with extreme rapidity on entering the blood stream may hold considerable promise for inhibition of thrombus formation, selective dilation of the vasculature, and other research and clinical applications.

Nitric oxide-releasing polymers containing the [N(O)NO]- group.

Ions of structure X[N(O)NO]- display broad-spectrum pharmacological activity that correlates with the rate and extent of their spontaneous, first-order decomposition to nitric oxide when dissolved. We report incorporation of this functional group into polymeric matrices that can be used for altering the time course of nitric oxide release and/or targeting it to tissues with which the polymers are in physical contact. Structural types prepared include those in which the [N(O)NO]- group is attached to heteroatoms in low molecular weight species that are noncovalently distributed throughout the polymeric matrix, in groupings pendant to the polymer backbone, and in the polymer backbone itself. They range in physical form from films that can be coated onto other surfaces to microspheres, gels, powders, and moldable resins. Chemiluminescence measurements confirm that polymers to which the [N(O)NO]- group is attached can serve as localized sources of nitric oxide, with one prototype providing sustained NO release for 5 weeks in pH 7.4 buffer at 37 degrees C. The latter composition, a cross-linked poly-(ethylenimine) that had been exposed to NO, inhibited the in vitro proliferation of rat aorta smooth muscle cells when added as a powder to the culture medium and showed potent antiplatelet activity when coated on a normally thrombogenic vascular graft situated in an arteriovenous shunt in a baboon's circulatory system. The results suggest that polymers containing the [N(O)NO]- functional group may hold considerable promise for a variety of biomedical applications in which local delivery of NO is desired.

V-PYRRO/NO: an hepato-selective nitric oxide donor improves porcine liver hemodynamics and function after ischemia reperfusion.

BACKGROUND: The role of nitric oxide (NO) in ischemia reperfusion (I/R) injury is controversial as both beneficial and harmful effects have been reported. We explored the potential role of a pharmacological agent recently shown to generate NO metabolically in the liver in an animal model of transplantation. METHODS: The effect of a selective hepatic NO donor, O2-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO), on hepatic hemodynamics and biliary function was evaluated in both the in situ and I/R pig liver. RESULTS: V-PYRRO/NO significantly reduced in situ hepatic vascular resistance (HVR) without altering systolic blood pressure. Portal vein flow was essentially unchanged during in situ infusions while hepatic artery flow nearly doubled (P=0.03). After I/R, V-PYRRO/NO infusions significantly reduced both portal vein pressure (PVP) and HVR (P=0.04). Also, serum bile acid clearance increased from 15% when taurocholate (TC) was infused alone to 46% (P=0.007) when infused simultaneously with V-PYRRO/NO. Aqueous bile production tripled with TC and V-PYRRO/NO as compared to TC alone (P=0.04). Analysis of bile outputs revealed a significant increase in biliary cholesterol, biliary phospholipid, and biliary bile acid (P<0.05) with V-PYRRO/NO infusion. CONCLUSIONS: The hepato-selective nitric oxide donor, V-PYRRO/NO, reduced hepatic resistance parameters of the pig liver both before and after I/R and improved the plasma clearance of bile acid and biliary outputs of bile acid-dependent compounds. The augmented function observed after I/R may be due to improvements in hepatic blood flow secondary to altered hepatic hemodynamics.

Carcinogenesis and mutagenesis by N-nitroso compounds having a basic center.

Two N-nitroso compounds that are derivatives of N,N-dimethylethylenediamine and are therefore strongly basic, were tested for carcinogenic activity. They were methylnitrosamino-N,N-dimethylethylamine (MNDMEA) and N,N-dimethylaminoethylnitrosoethylurea (DMENEU). Each was administered orally to male and female F344 rats by gavage. MNDMEA was also given by gavage to Syrian hamsters and to rats as a solution in drinking water. The response of rats treated with MNDMEA was almost the same by the two modes of treatment and all developed tumors of the esophagus and died in less than 40 weeks; many also had tumors of the nasal mucosa. Hamsters were less susceptible to the nitrosamine than rats, since they survived longer following a larger dose and the tumor incidence was small; several hamsters had tumors of the nasal mucosa, some males also had tumors of the liver and lung and one male and two females had a tumor of the colon. Although it is a strong directly acting mutagen, dimethylaminoethylnitrosoethylurea was weakly carcinogenic in rats, giving rise to tumors of the uterus and mammary gland in females, but having no particular target organ in male rats. The presence of a basic center in these N-nitroso compounds does not prevent their absorption nor their entry into cells, which they can transform to tumors.

Carcinogenesis by nitrosobis-(2-oxopropyl)amine labeled with deuterium and by nitroso-2-hydroxypropyl-2-oxopropylamine in rats and hamsters.

The effects of the labeling with deuterium of the alpha-methylene groups of the carcinogen nitrosobis-(2-oxopropyl)amine (NBOP) on its carcinogenic effectiveness in rats and hamsters have been studied. The greater strength of the C-D bond compared with the C-H bond often leads to slower metabolism and lesser carcinogenic activity. When NBOP and NBOP-d4 were given to male and female rats in drinking water at equimolar doses, the mortality rate from tumors was lower in the rats given the deuterium-labeled compound, although the results were statistically significant (P = 0.012) only in males. The incidences of tumors of several groups was similar for NBOP and NBOP-d4, but there was a marked difference between males and females, females having a high incidence of liver tumors, and males very few. When NBOP and NBOP-d4 were given by gavage to rats or Syrian hamsters at identical doses there was no difference in rate of mortality from tumors, or in the pattern of tumors induced by either compound. In rats, both compounds were given at two dose rates, and in neither was a difference seen. To complement the studies with NBOP, a normal reduction product formed metabolically in vivo, nitroso-(2-hydroxypropyl) (2-oxopropyl)amine (NHPOP) was administered to rats in drinking water at the same dose rate. In male rats, the mortality rate was lower with NHPOP than with NBOP, while with female rats the opposite was the case (P less than 0.01 in both cases) and there was little difference in the pattern of tumors induced in either sex. NHPOP appears to have a quite distinct carcinogenic effect from NBOP, suggesting that the metabolic conversion of one to the other does not play a large role. The weak deuterium-isotope effect of NBOP-d4 given to rats in drinking water, but not detected in rats or hamsters treated by gavage, suggests that alpha-oxidation of NBOP is not likely to be a rate-limiting step in carcinogenesis by NBOP.