Acute tobacco smoke exposure alters the profile of metabolites produced from benzo[a]pyrene by the isolated perfused rabbit lung

The influence of whole tobacco smoke or the gas phase from smoke on the metabolism of $\text{[}{}^{14}\text{C]benzo}\text{[a]}\text{pyrene}$ was e xamined using the isolated perfused rabbit lung model. Fresh whole tobacco smoke mixed with the air ventilating the perfused lung produces an immediate and dose related decrease in the metabolism of $\text{[}{}^{14}\text{C]benzo}\text{[a]}\text{pyrene}$. The metabolites of $\text{[}{}^{14}\text{C]benzo}\text{[a]}\text{pyrene}$, diols, quinones, phenols and polar compounds are generally decreased in quantity. At the lowest level of smoke administered the percentage of BP-7,8-diol produced is increased dramatically. The results indicate that one of the factors contributing to the carcinogenicity of tobacco smoke may be its ability to produce an immediate alteration in the pulmonary metabolism of polycyclic aromatic hydrocarbons.     

Adenosine receptor interactions and anxiolytics

$\text{[}{}^3\text{H}\text{]-N}{}^6\text{-}\text{cyclohexyladenosine}$ and [³H]-1,3-diethyl-8-phenylxanthine label the A₁ subtype of adenosine receptor in brain membranes. The affinities of methylxanthines in competing for A₁ adenosine receptors parallel their potencies as locomotor stimulants. The adenosine agonist N⁶-(-phenylisopropyl) adenosine is a potent locomotor depressant. Both diazepam and $\text{N}{}^6\text{-(}\text{l}\text{-}\text{phenylisopropyl}\text{)}\text{adenosine}$ cause locomotor stimulation in a narrow range of subdepressant doses. Combined stimulant doses of the two agents depress motor activity, as do larger doses of either one, given separately.Evidence supporting and against the hypothesis that some of the actions of benzodiazepines are mediated via the adenosine system is reviewed. A number of compounds interact with both systems, probably because of physico-chemical similarities between adenosine and diazepam. It is concluded that of the four classic actions of benzodiazepines, the sedative and muscle relaxant (but not anxiolytic or anticonvulsant) actions could possibly be mediated by adenosine.     

Extrapineal amine N-acetylation in rat brain: Regional and subcellular distribution and enzyme kinetics

Analysis by thin-layer chromatography showed that $\text{[}{}^{14}\text{C}\text{]N-}\text{acetyltryptamine and}\text{[}{}^{14}\text{C}\text{]N-}\text{acetyl}\text{-β-}\text{phenylethylamine}$ are formed from the incubation of [¹⁴C]acetyl-CoA with tryptamine or β-phenylethylamine. respectively, in the presence of rat brain extracts. The specific activity of the N-acetyltransferase in fifteen discrete regions of rat CNS ranged from 1.64 ± 0.05 nmoles of product formed/mg of protein/hr in cerebellum to 0.57 ± 0.05 nmole in occipital cortex with tryptamine as substrate, and from 2.80 ± 0.30 nmoles in cerebellum to 0.91 ± 0.13 nmole in cervical cord with β- phenylethylamine as substrate. Comparison of the regional specific activities in the presence of the respective substrates yielded a correlation coefficient of 0.83 (P < 0.01). In cerebellum N-acetyltransferase activity appears exclusively in cytosol. At two stages of purification (i.e. after Bio-Gel fractionation as well as after ammonium sulfate precipitation), the enzyme exhibited biphasic kinetics with respect to acetyl-CoA in the presence of tryptamine or β-phenylelhylamine and with respect to either substrate in the presence of acetyl-CoA.     

Inhalation studies on the biotransformation and elimination of [14C] trichlorofluoromethane and [14C] dichlorodifluoromethane in beagles

The possible biotransformation of trichlorofluoromethane (FC-11) and dichlorodifluoromethane (FC-12) was investigated in 4 male and 2 female adult Beagles after a short (6- to 20-min) inhalation. Dogs were anesthetized with ketamine and succinylcholine, intubated, and ventilated artificially. Trichlorofluoromethane (1000–5000 ppm, $\text{v}\text{v}$) or dichlorodifluoromethane 38000–12,000 ppm, $\text{v}\text{v}$) containing up to 180μ Ci of $\text{[}{}^{14}\text{C}\text{]}\text{fluorocarbon}$ was delivered from 110-liter Teflon bags, and all exhalations were collected via a nonrebreathing valve in similar bags for 1 hr. Venous blood samples were withdrawn at appropriate times and assayed for fluorocarbon-associated radioactivity. Exhalation bags were assayed for $\text{[}{}^{14}\text{C}\text{]}\text{fluorocarbon}$ and ¹⁴CO₂. Urine was collected for up to 3 days and assayed for ${}^{14}\text{C}$ metabolites as nonvolatile radioactivity. In some experiments animals were sacrificed 24 hr after exposure and tissues were removed for determination of nonvolatile radioactivity. Essentially all of the administered (inhaled) fluorocarbon was recovered in the exhaled air within 1 hr. Only traces of radioactivity were found in urine or exhaled carbon dioxide. All tissues contained measurable concentrations of nonvolatile radioactivity 24 hr after exposure but together represented less than 1% of the administered dose. It is not possible to determine if these trace levels are associated with metabolites of the fluorocarbons or with the unavoidable radiolabeled impurities present in the administered gas mixture. Neither phenobarbital pretreatment (60 mg/day for 3 days) nor prolonged exposure (50–90 min) produced any alteration of these results. Thus, it can be concluded that FC-11 and FC-12 are relatively refractory to biotransformation after a short inhalation exposure and that they are rapidly exhaled in their unaltered chemical form.     

Tissue distribution of histamine in a mutant mouse deficient in mast cells: Clear evidence for the presence of non-mast-cell histamine

The contents of histamine in various tissues of mutant mice deficient in mast cells ($\text{W}\text{W}{}^{\mathrm{v}}$) and in congenic normal mice (+/+) were determined by high-performance liquid chromatography and were compared. In spite of the absence of mast cells in $\text{W}\text{W}{}^{\mathrm{v}}$ mice, the histamine content of their whole bodies was about 5–10% of that of +/+ mice. The skin, heart and lungs of $\text{W}\text{W}{}^{\mathrm{v}}$ mice contained negligible amounts of histamine (about 2% of that in +/+ mice), but the liver, kidneys and spleen contained appreciable histamine (8–15% of that in +/+ mice), and the brain and stomach contained much histamine (45 and 34%, respectively, of that in +/+ mice). These results indicate the presence of non-mast-cell histamine, especially in the brain and stomach, where it may play important physiological roles.     

Excretion of THC and its metabolites in ewes' milk

After single iv injections of either 0.02 mg/kg or 1 mg/kg of $\text{[}{}^{14}\text{C}\text{]Δ}{}^9\text{-}\text{tetrahydrocannabinol}$, [¹⁴C]THC, to lactating ewes, radioactivity was detected in the milk at all subsequent time intervals tested (4–96 hr). Radioactivity was found in unchanged THC as well as in various unidentified metabolites. Only about 15% of the administered radioactivity was excreted by the ewes in the first 48 hr; most of this was in the urine and feces. Radioactivity appeared in the feces and urine of a lamb suckling milk from a ewe injected with [¹⁴C]THC, indicating transfer of THC and its metabolites via the milk. These results confirm previous literature reports indicating slow elimination of THC, and show that milk is an additional route of excretion.     

Effect of stannous chloride on rat femur

Oral administration of stannous chloride (SnCl₂) (1.0 mg $\text{Sn}{}^{\mathrm{2+}}\text{kg}$ body weight) to rats, twice daily for 30 or 90 days, caused a significant decrease of the calcium (Ca) content and acid phosphatase activity of the femoral epiphysis but did not reduce those of the femoral diaphysis. 1.0 mg $\text{Sn}{}^{\mathrm{2+}}\text{kg}$ for 30 days produced a significant decrease of alkaline phosphatase activity of the femoral epiphysis, but did not lower that of the femoral diaphysis. The results indicate that Sn may inhibit bone formation directly in the femoral epiphysis of rats.     

Mechanisms by which quipazine,a putative serotonin receptor agonist,alters brain 5-hydroxyindole metabolism

Quipazine (2-[1-piperazinyl] quinoline maleate) was shown to increase serotonin and decrease 5-hydroxyindoleacetic acid concentrations in whole brain, several brain regions, and the spinal cord of rats 1 hr after its administration (10 mg/kg, i.p.). In animals with transected spinal cords, quipazine induced stronger activation of extensor reflexes than 5-hydroxytryptophan, chlorimipramine, or Lilly 110140. This response could be blocked by methiothepin. In slices of rat cerebral cortex, quipazine inhibited the uptakes of [³H]-serotonin (EC₅₀ = 10^?6 M) and [³H]-norepinephrine ($\text{EC}{}_{50}\text{= 2 × 10}{}^{\mathrm{?6}}\text{m}$); it was equipotent with Lilly 110140 in inhibiting serotonin uptake, but less potent than chlorimipramine ($\text{EC}{}_{50}\text{= 10}{}^{\mathrm{?7}}\text{m}$). Quipazine administration to rats did not inhibit monoamine oxidase activity, and actually elevated brain tryptophan levels. These observations suggest that the effects of quipazine on brain serotonin and 5-hydroxyindoleacetic acid concentrations could have been caused by direct activation of central serotonin receptors (which would secondarily decrease impulse flow along serotonergic neurones), or by the inhibition of serotonin reuptake, or by both mechanisms.     

The effect of bencyclane on the oxidative phosphorylation in isolated mitochondria of heart and liver

Our experiments were designed to localize the inhibitory influence of bencyclane² on the process of oxidative phosphorylation in isolated heart and liver mitochondria. The following results were obtained: (1) The state-3-respiration of rat liver and rabbit heart mitochondria was inhibited by bencyclane. This inhibition was dependent on the substrate used as energy donator, being much more pronounced with glutamate $\text{(}\text{ed}{}_{50}\text{= 3.17 × 10}{}^{\mathrm{?8}}\text{or}\text{1.85 × 10}{}^{\mathrm{?7}}\text{moles/mg}$ of protein, respectively) than with succinate $\text{(}\text{ed}{}_{50}\text{= 3.4 × 10}{}^{\mathrm{?7}}\text{or}\text{4.78 × 10}{}^{\mathrm{?7}}\text{moles/mg}$ of protein, respectively). Since the 2,4-dinitrophenol stimulated respiration was equally inhibited, and glutamate transfer through the mitochondrial membrane not influenced, we assume the NADH-coenzyme-Q-reductase to be the site of interaction at the molecular level. (2) Bencyclane stimulates the state-4-respiration of isolated mitochondria with $\text{concentrations}\text{\$}\text{?}\text{= 10}{}^{\mathrm{?5}}\text{M}$. This effect depends on the molar bencyclane concentration of the incubation medium, and is not abolished by the addition of atractyloside, oligomycin or ruthenium red. Therefore, it is suggested that uncoupling of oxidative phosphorylation is the reason for this bencyclane effect. Theoretically, both of the described effects result in a reduction of the amount of ATP in the living cell. Possible consequences on myocardial function and the cardiovascular system are discussed in terms of previously published data in this field.     

The inhibitory action of ketamine HC1 on [3H]5-hydroxytryptamine accumulation by rat brain synaptosomal-rich fractions: comparison with [3H]catecholamine and [3H]gamma-aminobutyric acid uptake.

Ketamine HO was incubated with synaptosomal-rich fractions prepared from rat cerebral cortex to evaluate the effect of this agent upon the synaptosomal accumulation of [³H]5-HT. Accumulation of [³H]5-HT was shown to be reduced by ketamine in a concentration-related fashion. This action of ketamine was also found in synaptosomal rich fractions prepared from hypothalamus, corpus striatum, medulla oblongata and midbrain. Accumulation studies carried-out in the presence of reserpine and pargyline indicated that ketamine reduced the accumulation of [³H]5-HT through a competitive action on the synaptosomal membrane high affinity transport system (neuronal reuptake system). The effect of ketamine on the high affinity transport of [³H]NE, [³H]DA and [³H]GABA was also examined. The order of inhibition of transport by ketamine was [³H]5-HT >$\text{[}{}^3\text{H}\text{]}\text{DA}\text{= [}{}^3\text{H}\text{]}\text{NE}\text{> [}{}^3\text{H}\text{]}\text{GABA}$. These results show that ketamine is a potent and preferential inhibitor of the 5-HT neuronal reuptake system. The possible role of this action of ketamine, in the post anaesthetic excitatory response seen following the administration of ketamine, is discussed.     

Carbon disulphide tetratogenicity and postnatal effects in rat

Pregnant albino rats were exposed to carbon disulphide vapour in concentrations of 50, 100 or 200 $\text{mg}\text{m}{}^3$throughout gestation. Two successive generations (F₁ and F₂) were studied.Concentration levels of 100 and 200 $\text{mg}\text{m}{}^3$ produced marked dose-related impairment in the prenatal development of the F₁ progeny, with increase of early embryonal lethality, reduction in foetal weight and a high incidence of malformations affecting mostly the brain and limbs. Postnatal viability, body weight, lipid and energy metabolism and behaviour were also impaired. Behavioral deviations were observed even at 50 $\text{mg}\text{m}{}^3$.After reaching sexual maturity the F₁ rats were mated within their experimental groups, but no further carbon disulphide exposure was applied. The adverse effects on progeny were still detectable in the F₂ generation. Structural abnormalities of the same type as those found in the F₁ at 100 and 200 $\text{mg}\text{m}{}^3$ exposure were observed in their progeny and, postnatally, statistically significant behavioral changes were observed in the progeny of all test groups.     

Effect of polychlorinated biphenyls on the immune responses of rhesus monkeys and mice.

The relationship between lipid peroxidation, glutathione (GSH) content, and CCl₄-induced toxicity was investigated in rat hepatocytes isolated by a collagenase-perfusion technique. Two chemical initiators of lipid peroxidation, ferric ions complexed with adenosine diphosphate ($\text{ADP}\text{Fe}{}^{\mathrm{3+}}$) and diethyl maleate, were studied for comparison. CCl₄ caused a reduction of intracellular K⁺ and release of alanine aminotransferase (ALT) into the medium, but no evidence of lipid peroxidation, as measured by the absorbance of thiobarbituric acid (TBA)-reacting materials and lipid-extract diene conjugation. $\text{ADP}\text{Fe}{}^{\mathrm{3+}}$ caused lipid peroxidation, but only a small loss of K⁺. Diethyl maleate caused a greater amount of lipid peroxidation and cell damage than did $\text{ADP}\text{Fe}{}^{\mathrm{3+}}$. Neither response appeared to be related to the GSH content, which was reduced by diethyl maleate, but not by $\text{ADP}\text{Fe}{}^{\mathrm{3+}}$, and by CCl₄ only at the highest dose. The results suggest that lipid peroxidation is not a requisite step in CCl₄-induced toxicity in isolated hepatocytes.     

Studies on the respiratory uptake and excretion and the skin absorption of methyl n-butyl ketone in humans and dogs

Methyl n-butyl ketone (MnBK) has produced peripheral neuropathy in experimental animals and is implicated in an occupationally produced neuropathy. Since occupational exposure to MnBK is by inhalation or skin contact, both the absorption and elimination of MnBK vapor and its absorption through skin were investigated. Studies were carried out first with male beagle dogs and subsequently with human volunteers. Humans exposed for 7.5 hours to 10 or 50 ppm or for 4 hr to 100 ppm of MnBK vapor absorbed between 75 and 92% of the inhaled vapor. Unchanged MnBK was not eliminated extensively in the postexposure breath or in urine. 2,5-Hexanedione, a metabolite of MnBK known to be neurotoxic in rats, was found in the serum of humans exposed to either 50 or 100 ppm of MnBK. The absorption and elimination of MnBK in dogs was similar to that observed in humans. The skin absorption of [1-¹⁴C]MnBK or a $\text{9}\text{1}$ ($\text{v}\text{v}$) mixture of methyl ethyl ketone $\text{(MEK)}\text{[1-}{}^{14}\text{C]MnBK}$ was determined by excretion analysis. Two volunteers exposed by skin contact to [1-¹⁴C]MnBK absorbed 4.8 μg min^?1 cm^?2 and 8.0 μg min^?1 cm^?2, respectively. Skin exposure to $\text{MEK}\text{[1-}{}^{14}\text{C]MnBK}$ resulted in the respective absorption of 4.2 and 5.6 μg min^?1 cm^?2 by two individuals. Two volunteers given an oral dose of [1-¹⁴C]MnBK (2 μCi; 0.1 mg/kg) excreted 49.9 and 29.0% of the dose, respectively, as respiratory ¹⁴CO₂ within 3 to 5 days and 27.6 and 25.0% of the dose, respectively, in urine within 8 days. Both [1-¹⁴C]MnBK and $\text{MEK}\text{[1-}{}^{14}\text{C]MnBK}$ were absorbed through the skin of dogs. These findings show that MnBK is readily absorbed by the lungs, the gastrointestinal tract, and through the skin, is not eliminated extensively unchanged in breath or urine, and is metabolized to CO₂ and 2,5-hexanedione. Radioactivity derived from [1-¹⁴C]MnBK was excreted slowly by man, suggesting that repeated daily exposure to high concentrations of MnBK may lead to a prolonged exposure to neurotoxic metabolites.     

The effects of cadmium, manganese and aluminium on sodium-potassium-activated and magnesium-activated adenosine triphosphatase activity and choline uptake in rat brain synaptosomes

The effects of Cd²⁺, Mn²⁺ and Al³⁺ on rat brain synaptosomal sodium-potassium-activated and magnesium-activated adenosine triphosphatase (Na-K-ATPase and Mg-ATPase) activity and choline uptake were studied. All three types of metal ions inhibited Na-K-ATPase activity more markedly than Mg-ATPase activity. The rank order of inhibition of Na-K-ATPase was: $\text{Cd}{}^{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 5.4 μ}\text{M}\text{) >}\text{Mn}{}_{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 955 μ}\text{m}\text{) >}\text{Al}{}^{\mathrm{3+}}\text{(}\text{ic}{}_{50}\text{= 8.3}\text{mM}$). The rank order of inhibition of Mg- was:$\text{Cd}{}^{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 316 μ}\text{M}\text{>}\text{Mn}{}^{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 5.5}\text{mM}\text{>}\text{Al}{}^{\mathrm{3+}}\text{(}\text{ic}{}_{50}\text{= 21.9}\text{mM}\text{).}\text{Al}{}^{\mathrm{3+}}$ was most potent in inhibiting synaptosomal choline uptake ($\text{ic}{}_{50}\text{= 24μ}\text{M}$ in the absence of Ca²⁺ and 123 μ.M in the presence of 1 mM Ca²⁺). $\text{Cd}{}^{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 363 μ}\text{M}\text{)}$ was a more effective inhibitor of choline uptake than $\text{Mn}{}^{\mathrm{2+}}\text{(}\text{ic}{}_{50}\text{= 1.2?1.5}\text{mM}\text{)}$ . The presence of 1 mM Ca²⁺ did not alter choline uptake, nor did it antagonize the inhibitory actions of the three metals. Our observations that Cd²⁺ and Al³⁺ inhibited synaptosomal choline uptake, but did not show parallel inhibitory effects on Na-K-ATPase activity directly contradicts the ionic gradient hypothesis. These results are also discussed in relation to the in vivo neurotoxicity of cadmium, manganese and aluminium.     

Determination of extraction constant,true partition coefficient and formation constant of ion-pair complexes of quaternary ammonium salts,tetrabutylammonium bromide and isopropamide iodide.with some organic anions by a solvent extraction technique

A new method of determining the extraction constant (K_e, the true partition coefficient (TPC) and the formation constant (K_f) of ion-pairs, was developed by the solvent extraction technique. K_e and TPC were estimated from the reciprocals of the intercept and the slope of the regression line obtained by plotting

$\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{APC ? dA}\text{vs}\text{B}\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{dA}\text{APC ? dA}\text{+}\text{A}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{+}\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}$

in the following equation.

$\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{APC ? dA}\text{=}\text{1}\text{K}{}_{\mathrm{e}}\text{+}\text{B}\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{dA}\text{APC ? dA}\text{+}\text{A}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{+}\text{B}{}^{\mathrm{T}}{}_{\mathrm{W}}\text{x}\text{1}\text{TPC}$

where [A^T_W] and [B^T_W] are the total concentrations of the cationic compound A and that of the anionic compound B in the aqueous phase respectively, APC is the apparent partition coefficient of A, dA is the partition coefficient of cation A⁺. K_f, which is expressed by K_e/TPC, was then calculated. These constants were determined for the ion-pair extraction of tetrabutylammonium bromide and isopropamide iodide with 4 organic anions, i.e. benzoic acid, p-toluenesulfonic acid, salicylic acid and taurodeoxycholic acid. This new method might be applicable to other ion-pairs without further assumptions except that the molar ratio of the ion-pair formation be 1 : 1.     

Turnover of liver proteins in Phenoclor DP6-treated rats.

The effect of a diet containing Phenoclor DP6 on the average turnover of protein in subcellular fractions of the liver was studied in young rats. In experiment A, rats were given an intraperitoneal injection of $\text{[}{}^{14}\text{C}\text{]-}\text{guanidinolabeled}$ arginine, were then fed a diet containing 100 ppm of Phenoclor DP6 for 24 h, and then resumed a control diet. In experiment B rats were fed a DP6 diet for 4 days prior to receiving the isotope injection, and then resumed the DP6 diet for the entire experiment. Afterward, these rats were killed 1, 3, 5, and 8 days after pulse-labeling. Mitochondrial, microsomal, microsomal membrane, and ribosomal fractions were prepared from their livers, and these fractions were analyzed for acid-precipitable protein and radioactivity. Our results indicate no significant difference in the average rates of ${}^{14}\text{C}$ degradation between rats receiving a single DP6 dose and the control group. In rats ingesting a DP6 diet every day, the half-lives of total liver proteins were significantly shorter than in the control group. This difference is perhaps due to the rate of breakdown of the microsomal proteins. We found that in the microsomal fraction only the microsomal membrane proteins were affected by the DP6 treatment. Our results suggest that under our experimental conditions microsomal membrane protein metabolism (synthesis and breakdown) is enhanced by DP6 ingestion.     

The Ah regulatory gene product. Survey of nineteen polycyclic aromatic compounds' and fifteen benzo[a]pyrene metabolites' capacity to bind to the cytosolic receptor

The capacity of 19 polycyclic aromatic compounds and 15 benzo[a]pyrene metabolites to displace $\text{[1,6-}{}^3\text{H}\text{]2,3,7,8-}\text{tetrachlorodibenzo}\text{-p-}\text{dioxine}\text{([}{}^3\text{H]Tcdd}\text{)}$ from the mouse liver cytosolic Ah receptor was examined. We compared our data with various parameters taken from previously published results: the capacity of seven polycyclic hydrocarbons to induce aryl hydrocarbon hydroxylase (AHH) activity in human cell cultures, the capacity of 10 polycyclic hydrocarbons to induce azo dye N-demethylase activity in rat liver, the capacity of 6 polycyclic hydrocarbons to shorten zoxazolamine paralysis times in the intact rat, and the capacity of 15 benzo[a]pyrene metabolites to induce AHH activity in rat hepatoma H-4-II-E cultures. An excellent correlation is seen between the capacity to displace the radioligand from the Ah receptor and the capacity to induce these monooxygenase activities. Differences in the rate of cellular uptake and formation of alkali-extractable metabolites of dibenzo[a,h]anthracene, 3-methylcholanthrene, and benzo[a]anthracene in Hepa-1 mouse hepatoma cell cultures do not account for differences in the capacity of these three polycyclic hydrocarbons to displace [³H]TCDD from the Ah receptor.