Tumor promoters and cell transformation.
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Animals↗
Biomedical subjects
L Diamond
Publications and source records attributed to L Diamond.
Mutagenic activity of methyl- and fluoro-substituted derivatives of polycyclic aromatic hydrocarbons in a human hepatoma (HepG2) cell-mediated assay.
Several series of methyl- and fluoro-substituted polycyclic aromatic hydrocarbon (PAH) derivatives were tested for mutagenic activity in cell-mediated assays with cells of the human hepatoma cell line, HepG2, as PAH activators. The mutagenic activity of dibenz[a,h]anthracene [DB(a,h)A] increased progressively with the substitution of a methyl group at one or both non-benzo bay-region sites. At a concentration of 0.25 micrograms/ml, the mutation frequencies induced by DB(a,h)A, and 7,14-diMeDB(a,H)A were 1.3, 13.1 and 59.0 6-thioguanine-resistant colonies/10(5) viable V79 cells, respectively. Methyl groups at non-benzo bay-region sites in 3-methylcholanthrene and benzo[e]pyrene had little effect on mutagenic activity at the highest concentration which could be tested (2 micrograms/ml). The presence of a fluorine atom on the bay-region A-ring of 7,12-dimethylbenz[a]anthracene (DMBA) drastically drastically reduced mutagenic activity. At a concentration of 1.0 micrograms/ml, the mutation frequencies induced by DMBA, 1-fluoro-DMBA and 4-fluoro-DMBA were 50.5, 6.8 and 1.6, respectively. On the other hand, the mutation frequency was increased 6-fold when the fluoro substituent was in the 10-position of the D-ring of DMBA. Thus, for the most part, the relative mutagenic activities of these compounds in the HepG2 cell-mediated assay paralleled their skin tumor-initiating activity in SENCAR mice reported earlier (DiGiovanni et al., 1982, 1983a, b). These studies demonstrate the value of the HepG2 cell line as an exogenous, intact human cell activation system in short-term assays designed to evaluate the genotoxic effects of PAHs.
9,10-Dimethyl-1,2-benzanthracene↗
Chronic administration of water soluble tobacco smoke extract or nicotine fails to influence porcine coronary artery reactivity.
To determine if tobacco smoke components directly influence coronary vascular reactivity, we evaluated the contractile effects of prostaglandin (PG)F2 alpha and hypertonic KCl in porcine isolated left anterior descending coronary arteries derived from animals chronically treated (18 weeks) with either water soluble tobacco smoke extract, nicotine alkaloid, or saline. Dosing protocols for the extract and for nicotine were designed to achieve blood levels of nicotine approximating those attained by consumption of 2 packs/day of University of Kentucky 2Rl reference cigarettes. Histochemical evaluation of the arteries indicated that both the extract and nicotine caused expected increases in the collagen content of the tunica media. Neither the water soluble extract nor pure nicotine significantly altered coronary vascular sensitivity (as expressed by the ED50) to KCl or PGF2 alpha. Similarly, neither treatment altered the maximum contractile responses (determined as the tension developed normalized to mg wet wt) evoked by KCl and PGF2 alpha. These results indicate that prolonged exposure to water soluble components of tobacco smoke, in doses sufficient to elevate the collagen content of the coronary vascular wall, do not have direct effects on coronary reactivity to selected vasoconstrictor stimuli.
Animals↗
DBA/2 mice are as sensitive as SENCAR mice to skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate.
Mice of the inbred strain DBA/2 responded to a two-stage, initiation-promotion tumorigenesis protocol when high initiating doses (400 nmol/mouse) of 7,12-dimethylbenz[a]anthracene were utilized. They also responded when N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used as the initiating agent. The tumor response in both cases was characterized by a rapid rate of tumor development with the maximal tumor responses reached on or before the 15th week of promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). When DBA/2 mice were compared with SENCAR mice for promotion sensitivity following initiation with MNNG, the two mouse stocks responded with a nearly identical tumor response. C57BL/6 mice were essentially resistant to TPA promotion regardless of the initiator or the dose of initiator used. A preliminary study was conducted to determine how susceptibility to tumor promotion by TPA was inherited in F1 mice derived from DBA/2 (sensitive) and C57BL/6 (resistant) parents. The B6D2F1 mice were as sensitive as the DBA/2 parent, suggesting that susceptibility in these two inbred mouse strains is inherited as an autosomal dominant trait. The results show that these two inbred mouse strains may provide a model system for studying genetic factors controlling susceptibility to phorbol ester skin tumor promotion.
9,10-Dimethyl-1,2-benzanthracene↗
Relaxation of cat tracheobronchial and pulmonary arterial smooth muscle by vasoactive intestinal peptide: lack of influence by peptidase inhibitors.
Vasoactive intestinal peptide (VIP) caused concentration-dependent relaxation in precontracted segments of trachea, hilar bronchus, intrapulmonary bronchus and intrapulmonary artery (IPA) isolated from cat lungs. VIP-induced relaxation responses were abolished by preincubation of tissues with the proteolytic enzyme, alpha-chymotrypsin (2 units ml-1). At the concentration employed, alpha-chymotrypsin treatment did not adversely affect tissue viability as isoprenaline and bethanechol continued to relax airways and IPA, respectively. Aprotinin prevented enzymatic degradation of VIP by alpha-chymotrypsin as demonstrated by the ability of VIP to relax tissues incubated with both the peptidase inhibitor and alpha-chymotrypsin. A spectrum of peptidase inhibitors, including aprotinin, leupeptin, bestatin, bacitracin, beta-phenylpropionic acid and captopril, individually or in combination, did not augment the relaxant effects of VIP in isolated pulmonary tissues. These results suggest that local enzymatic degradation may not be a primary route for inactivation of VIP in cat isolated airways and IPA. If VIP acts as a neurotransmitter in these tissues, a mechanism other than enzymatic proteolysis may be responsible for terminating its action.
Airway Resistance↗
Comparison of vasoactive intestinal peptide and isoproterenol relaxant effects in isolated cat airways.
Vasoactive intestinal peptide (VIP), an endogenous peptide found in mammalian tissues including the lung, is a potent relaxant of smooth muscle. In precontracted segments of cat trachea, hilar bronchus, and intrapulmonary bronchus, concentration-relaxation curves to VIP were compared with those produced by isoproterenol. VIP and isoproterenol were nearly equipotent in causing relaxation of extrapulmonary airways. A decreasing sensitivity to VIP was observed in progressively smaller airways, suggesting regional variation in VIP-induced responses. In contrast, tissues showed no regional differences in response to isoproterenol. Propranolol (10(-6) M), which antagonized relaxation responses to isoproterenol, had no effect on VIP concentration-response curves. Indomethacin (10(-5) M) completely prevented responses to exogenous arachidonic acid but did not inhibit VIP-induced relaxation. Avian pancreatic polypeptide, which has been reported to inhibit vasodilator responses to VIP in the cat, was unable to antagonize airway smooth muscle relaxation induced by VIP. These results demonstrate that VIP is a potent relaxant of cat tracheobronchial smooth muscle in vitro and that the relaxant effects of this peptide are not mediated through beta-adrenergic receptors or by prostaglandins. In view of previous reports on the localization of VIP immunoreactivity in nerves around airways in cat lung, results of the present study suggest that VIP may participate in the regulation of airway tone in this species.
Animals↗
Neural control of relaxation in cat airways smooth muscle.
Functional innervation of cat airways smooth muscle was examined in isolated segments of trachea and bronchi using electrical field stimulation (EFS) techniques. Field stimulation caused contraction in tissues at resting tone and biphasic responses (contraction followed by relaxation) in tissues precontracted with 5-hydroxytryptamine (5-HT). Contractions were abolished by 10(-6) M atropine. Inhibitory responses were dependent on impulse voltage, duration, and frequency. At low voltages (less than or equal to 10 V) and pulse durations (less than or equal to 0.3 ms), EFS induced relaxations were abolished by 3 X 10(-6) M tetrodotoxin (TTX). Greater stimulus parameters elicited TTX-resistant relaxations. Pretreatment of the tissues with 10(-6) M propranolol and 10(-5) M guanethidine caused rightward shifts in relaxation frequency-response curves. These findings indicate that cat airways are innervated by excitatory cholinergic, inhibitory adrenergic, and inhibitory nonadrenergic noncholinergic (NANC) nerves. Pretreatment of the tissues with hexamethonium, cimetidine, indomethacin, or nordihydroguaiaretic acid did not affect NANC relaxation responses. It is concluded that NANC inhibitory responses in cat airway smooth muscle are mediated through intrinsic postganglionic nerve fibers and occur independently of histamine H2-receptor activation and without involvement of cyclooxygenase or lipoxygenase products of arachidonic acid metabolism.
Animals↗
The role of nicotine in the pathogenesis of pulmonary emphysema.
An investigation was undertaken to evaluate the potential role of nicotine in the pathogenesis of pulmonary emphysema. The acute lethality and the pulmonary toxicity of a single endotracheally administered dose of nicotine were studied in Long-Evans rats. The 24-h LD50 of nicotine was established at 19.3 +/- SD 5.4 mg/kg. Subsequently, rats were treated with either nicotine alone (3 or 7.5 mg/kg), porcine pancreatic elastase (PPE) alone (200 IU/kg) or PPE (200 IU/kg) followed 5 days later by nicotine (3 mg/kg). The selected dose of PPE was below the threshold dose for induction of emphysematous lesions. Cage and sham-treated control groups also were included in the investigation. Four weeks after treatment, extensive physiologic tests were conducted to evaluate the ventilatory, mechanical, and gas exchange functions of the lungs. Lung tissue specimens also were taken for estimation of tissue volume density. Although a few isolated incidents of significant intergroup differences were observed, no distinctive pattern of functional or structural change reminiscent of emphysema was noted in any of the experimental groups. It is concluded that endotracheal instillation of a single, relatively high, dose of nicotine neither induces nor augments the development of pulmonary emphysema in the rat.
Animals↗
Comparative effects of inhaled isoproterenol and vasoactive intestinal peptide on histamine-induced bronchoconstriction in human subjects.
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Adult↗
Benzo(e)pyrene-induced alterations in the metabolic activation of benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene by hamster embryo cells.
Benzo(e)pyrene (BeP) is a cocarcinogen with benzo(a)pyrene (BaP) and an anticarcinogen with 7,12-dimethylbenz(a)anthracene (DMBA) in mouse skin initiation-promotion assays (Slaga, T.J., Jecker, L., Bracken, W.M. and Weeks C.E. Cancer Lett. 7: 51-59, 1979). We have investigated the effects of BeP on the metabolic activation of BaP and DMBA in early-passage cultures of Syrian hamster embryo cells. BeP had no effect on BaP-induced mutation frequencies in hamster embryo cell-mediated assays with V79 target cells. However, it inhibited the DMBA-induced mutagenesis by as much as 10-fold at the highest dose tested. Low doses of BeP did not affect the total amount of BaP metabolized, but the proportion of water-soluble metabolites was reduced, and the proportions of trans-7,8-dihydro-7,8-dihydroxybenzo(a)pyrene and trans-9,10-dihydro-9,10-dihydroxybenzo(a)pyrene were increased. Higher doses did decrease BaP metabolism and caused similar alterations in the metabolite profile. In cultures treated with trans-7,8-dihydro-7,8-dihydroxybenzo(a)pyrene, BeP greatly reduced the oxidative metabolism of this diol. BeP inhibited DMBA metabolism at all doses tested; the proportion of water-soluble metabolites formed was decreased, and the proportions of trans-8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz(a)anthracene and trans-3,4-dihydro-3,4-dihydroxy-7,12-dimethylbenz(a)anthracene were increased. The results demonstrate that BeP is an effective inhibitor of the secondary oxidation of carcinogenic hydrocarbon diols required to convert diols which are proximate carcinogens to ultimate carcinogens such as diol-epoxides. The balance between (a) limited inhibition with consequent increase in total exposure to the ultimate carcinogenic form and (b) sufficient inhibition to reduce exposure to the ultimate carcinogenic form may determine whether BeP acts as a co- or anticarcinogen with a particular carcinogenic hydrocarbon.
9,10-Dimethyl-1,2-benzanthracene↗
Comparison of the metabolic activation of 7, 12-dimethylbenz(a)anthracene by a human hepatoma cell line (HepG2) and low passage hamster embryo cells.
Under similar conditions of cell-mediated mutagenesis, secondary hamster embryo (HE) cells were much more effective than were cells of the human hepatoma cell line, HepG2 , in activating 7, 12-dimethylbenz(a)anthracene (DMBA) to metabolites mutagenic for V79 Chinese hamster cells. At the same dose of DMBA (0.1 microgram/ml), mutation induction (6-thioguanine resistance) with HE cells as activators was about ten times greater than with HepG2 cells as activators. Both cell types rapidly metabolized DMBA. HepG2 cells converted DMBA primarily to water-soluble derivatives that were neither sulfates nor glucuronides, whereas HE cells converted DMBA to a variety of organic solvent-soluble and water-soluble metabolites. The major water-soluble metabolites produced by HE cells were phenol-glucuronides. In HepG2 cells, binding of DMBA to DNA reached a maximum value of 12.1 pmol/mg DNA at 12 hr, whereas in HE cells, binding reached a peak value of 180.7 pmol/mg DNA at 24 hr. Despite this difference in total binding between the two cell types, the pattern of DNA adducts formed was nearly identical. The results indicate that the marked difference in the ability of HepG2 and HE cells to activate DMBA in cell-mediated mutation assays is not due to a lower metabolizing capacity of HepG2 cells for DMBA. Rather, significant differences in the metabolic pathways used by the two cell types lead to a marked reduction in DNA-binding metabolites in one cell type ( HepG2 ) compared to the other (HE).
9,10-Dimethyl-1,2-benzanthracene↗
Effect of inhaled diphemanil methylsulfate, a parasympatholytic agent, on histamine induced bronchoconstriction in asymptomatic asthmatics.
Parenterally administered diphemanil methylsulfate, a quarternary ammonium compound with both parasympatholytic and direct bronchial smooth muscle relaxing properties, has been found effective in the treatment of bronchial asthma. The present study was undertaken to test the effectiveness of inhaled diphemanil in preventing histamine induced bronchoconstriction in asymptomatic adult asthmatics. Twenty subjects, aged 19-40 years (average 25) were studied, each on three different days, observing an interval of at least 70 hours between testing. On day one, airway sensitivity to inhaled histamine was determined. On days two and three, histamine challenge was repeated 20 minutes after inhalation of either diphemanil (2 mg) or its vehicle in a double-blind crossover design. Airway sensitivity was assessed by determining cumulative log dose units of inhaled histamine required to provoke a 20% decline in FEV1 (log PD20 - FEV1). Diphemanil did not prevent histamine induced bronchoconstriction nor did it significantly affect log PD20 - FEV1 (p = 0.59). We conclude that a 2 mg dose of diphemanil, administered by oral inhalation 20 minutes before histamine challenge, is ineffective in protecting against induced bronchospasm in asymptomatic adult asthmatics.
Administration, Intranasal↗
A simple technique for cold air and exercise challenge to assess bronchial reactivity: the effects of acute coryzal rhinitis on airway reactivity.
The bronchoconstrictor response to exercise which occurs in asthmatics can be enhanced by the simultaneous inhalation of cold air. We describe here a simple technique for the delivery of sub-freezing inspired air during exercise. We have examined airway function at rest and following cold air/exercise challenge in 24 healthy young adults during acute coryzal rhinitis and six weeks later. There were no clinically significant changes in baseline airway function or airway responsiveness to cold air/exercise in association with acute coryzal rhinitis.
Adult↗
Relaxant effects of vasoactive intestinal peptide and bethanechol in cat intrapulmonary artery.
The relaxant actions of vasoactive intestinal peptide (VIP) and bethanechol were examined on ring segments of intrapulmonary artery (IPA) isolated from cat lung. On a molar basis, VIP was 75 times more potent than bethanechol; however, VIP was less efficacious than bethanechol in reversing phenylephrine induced tone. Responses to VIP were unaffected by pretreatment of the tissues with atropine, indomethacin or avian pancreatic polypeptide. These results suggest that VIP may participate in the regulation of pulmonary vascular smooth muscle tone through a potent relaxant action that occurs independent of muscarinic cholinergic receptor activation or liberation of prostaglandins.
Animals↗
Time-dependent differences in the benzo[a]pyrene-DNA adducts present in cell cultures from different species.
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Animals↗
A technique for measuring the perception of added resistive loads during nasal breathing.
The perception of resistive loads added to nasal breathing was assessed in ten healthy adults using established psychophysical methods previously described for oral breathing. Detection threshold, that is, the smallest incremental resistance that the subject could detect 50% of the time, was determined at three different time periods (0, 30, and 60 min) on two separate days to determine the reproducibility of values over time. Nasal airway resistance measurements were made before and after threshold determinations to determine the influence of baseline resistance on the ability to detect added loads as well as to assess any effects of the procedure itself on resting nasal airway resistance. Analyses of the data revealed that subject-to-subject differences were the largest source of variability in threshold values followed by time period-to-time period differences and day-to-day variability. Although it was the smallest variability source, day-to-day variability still was significantly greater than zero. In contrast to previously published reports on resistive load detection during mouth breathing, the degree of baseline resistance did not appear to influence the subject's ability to detect added resistive loads during nasal breathing. These techniques may provide a methodological basis for objectively evaluating the effects of pharmacologic agents on perceived nasal patency.
Adult↗
Enhancement of the skin tumor-initiating activity of polycyclic aromatic hydrocarbons by methyl-substitution at non-benzo 'bay-region' positions.
The effect of substituting a methyl group at the non-benzo 'bay-region' site of several polycyclic aromatic hydrocarbons on skin tumor-initiating activity was determined. A methyl group at this position enhanced the tumor-initiating activity of dibenz[a,h]anthracene, 3-methylcholanthrene and 7-methyldibenz[a,j]anthracene, but not of dibenz[a,c]anthracene. 2,3,7,8-Tetrachlorodibenzo-p-dioxin was an effective inhibitor of skin tumor initiation by 7,14-dimethyldibenz-[a,h]anthracene and 3,6-dimethylcholanthrene. There appears to be a general rule regarding methyl-substituted hydrocarbons: where a 'bay-region' exists in a polycyclic aromatic hydrocarbon molecule, methyl-substitution at the non-benzo 'bay-region' site results in enhanced tumor-initiating activity. The effect of methyl substitution in this position can be most simply explained as due to enhancement of the reactivity of the benzo ring through distortion of the aromatic ring system from planarity. The consequences of this effect are discussed.
Animals↗
Tumor initiating activity of 9- and 10-fluoro-7,12-dimethylbenz[a]-anthracene (DMBA) and the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on tumor initiation by monofluoro derivatives of DMBA in SENCAR mice.
We have determined the skin tumor initiating activity in SENCAR mice of 6 monofluoro derivatives of 7,12-dimethylbenz[a]anthracene (DMBA). 9-Fluoro-DMBA (9-F-DMBA) was approximately as active, and 10-F-DMBA was more active than the parent hydrocarbon, DMBA. The difference between DMBA and 10-F-DMBA was most dramatic at the highest initiating doses of 10-F-DMBA tested. 4-F-DMBA, which was only weakly active as an initiator, was also tested as a complete carcinogen on mouse skin; after 30 weeks of treatment, 50- and 100-nmol weekly doses failed to elicit papillomas or carcinomas. Animals treated with 50 nmol of DMBA weekly exhibited a 100% papilloma incidence and a 42% carcinoma incidence. Pretreatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) effectively inhibited tumor initiation with all of the monofluoro derivatives of DMBA tested. The ED50 (dose of TCDD producing half-maximal inhibition) for the inhibition of DMBA initiation in SENCAR mice was determined to be 1.8 X 10(-3) micrograms/mouse (5.6 pmol). The results indicate that the introduction of a fluorine atom in ring D of DMBA has no effect (positions 9 and 11) or enhances (position 10) tumor initiating activity. We believe 10-F-DMBA to be the first example of a hydrocarbon with a fluoro substituent giving rise to increased tumor initiating activity. The results also indicate that structural modifications that alter tumor initiating activity do not alter the ability of TCDD to inhibit tumorigenesis by DMBA.
9,10-Dimethyl-1,2-benzanthracene↗