Cysteine-S-sulfate: brain damaging metabolite in sulfite oxidase deficiency

Cysteine-S-sulfate is an abnormal metabolite discovered in the urine and blood of a patient with cysteine oxidase deficiency, a rare disorder of sulfur amino acid metabolism associated with brain damage and mental retardation. The molecular structure of cysteine-S-sulfate closely resembles that of glutamate and related acidic amino acids which have both neuroexcitatory and neurotoxic properties (excitotoxic amino acids). Here we demonstrate that cysteine-S-sulfate induces the glutamate type of neuropathology in the rat central nervous system when administered subcutaneously to infants or intracerebrally to adults. It is postulated that cysteine-S-sulfate may be the neurotoxic agent responsible for brain damage in sulfite oxidase deficiency. The possibility that other excitotoxic amino acids could play occult roles in other unexplained neuropathologic conditions is discussed.

Genetic effects of dimethyl sulfate, diethyl sulfate, and related compounds

DMS and DES are monofunctional alkylating agents that have been shown to induce mutations, chromosomal aberrations, and other genetic alterations in a diversity of organisms. They have also been shown to be carcinogenic in animals. As an alkylating agent, DMS is a typical SN2 agent, attacking predominantly nitrogen sites in nucleic acids. DES is capable of SN1 alkylations as well as SN2 and thereby causes some alkylation on oxygen sites including the O6-position of guanine which is thought to be significant in mutagenesis by direct mispairing. The mutagenicity of DMS is better explained in terms of indirect, repair-dependent processes. With respect to both alkylating activity and genetic effects, striking similarities are found between DMS and MMS and between DES and EMS. In most systems where they have been tested, both DMS and DES are mutagenic. Results of many of the mutagenesis studies involving these compounds and other alkylating sulfuric acid esters are summarized in Tables 6, 7, 8, 9 and 10 of this review. Most data are consistent with these agents acting primarily as base-pair substitution mutagens. In the case of DES, strong specificity for G.C to A.T transitions has been reported in some systems but has not been clearly supported in some others. Low levels of frameshift mutations of the deletion type are also likely. In addition to the induction of mutations, recombinogenic and clastogenic effects have been described.

Long-term exposure to sulfur dioxide, sulfuric acid mist, fly ash, and their mixtures. Results of Studies in Monkeys and guinea pigs

Groups of cynomolgus monkeys and guinea pigs were exposed to mixtures of sulfur dioxide, fly ash, and sulfuric acid mist. The exposure concentrations varied between 0.1 and 5.0 ppm for sulfur dioxide, 0.1 and 1 mg/cu m for sulfuric acid mist, while a concentration of approximately 0.5 mg/cu m was used for fly ash. The duration of exposure was 52 weeks for guinea-pigs and 78 weeks for monkeys. Pulmonary function tests and serum biochemical and hematological analyses were conducted prior to and periodically during the exposure period. At the termination of exposure, the lungs were examined microscopically. Analysis of the data revealed that in groups exposed to the mixtures of pollutants, sulfuric acid mist was responsible for the effects observed. No synergistic action between the pollutants was detected.

Physiological and histological alterations in the bronchial mucociliary clearance system of rabbits following intermittent oral or nasal inhalation of sulfuric acid mist

Rabbits were exposed to submicometer sulfuric acid mist (H2SO4) for 1 h/d, 5 d/w for 4 wk, during which time mucociliary clearance was monitored by external in vivo measurements of tagged tracer aerosol retention. One group was exposed orally to 250 micrograms/m3, another to the same concentration via the nose, and a third to 500 micrograms/m3 also via nasal breathing. Clearance was accelerated on specific individual days during the course of the acid exposures, especially at 500 micrograms/m3. In all series, clearance was significantly faster, compared to preexposure controls, during a 2-wk follow-up period after acid exposures had ceased. At the end of this period, the rabbits were sacrificed, and histological sections were obtained from the tracheobronchial tree. Significantly increased epithelial thickness of small conducting airways, compared to sham exposure controls, occurred in rabbits exposed orally at 250 micrograms/m3 or nasally at 500 micrograms/m3, and additionally the lumen of the smallest airways of the former group was narrower than control. The number of airways containing epithelial secretory cells was also significantly greater in these acid exposure groups compared to sham controls. The only change in the rabbits exposed nasally at 250 micrograms/m3 was a significant increase in the number of airways with epithelial secretory cells in the smallest airway classification. The histological alterations provide a basis for observed changes in clearance, and are similar to those found in chronic bronchitis in humans and experimental animals. Differences in site and degree of histological response and degree of physiological change between the two groups exposed to identical acid concentrations appear to have been due to differences in exposure mode, with resultant effects on breathing pattern, aerosol size distribution, and concentration penetrating beyond the upper respiratory tract to specific lung sites.

Decontamination procedures for skin exposed to phenolic substances

Spraying or swabbing with a mixture of polyethylene glycol 300/industrial methylated spirits (PEG-300/IMS) (2:1 by volume) has been shown to substantially reduce mortality, systemic effects, and skin burns resulting from skin contamination by phenol, cumene hydroperoxide, or phenol/acetone cleavage product. The skin-damaging potentials of sodium hydroxide and sulfuric acid have also been investigated. PEG-300/IMS(2:1 by volume) mixture was found, in rats, to be slightly less effective than water as means of decontamination. The PEG-300/IMS mixture has been shown not to cause eye irritation, and so should not present a hazard where this mixture is used as a decontaminant spray.

The use of a retrievable self-expanding stent in treating childhood benign esophageal strictures

BACKGROUND/PURPOSE

Esophageal stenting is a popular form of treatment of esophageal strictures in adults but is not widely used in children. The aim of the current study was to investigate whether esophageal stents could be used safely and effectively in the treatment of esophageal stenosis in children.

METHODS

Covered retrievable expandable nitinol stents were placed in 8 children with corrosive esophageal stenosis. The stents were removed 1 to 4 weeks after insertion.

RESULTS

The stents were placed in all patients without complications and were later removed successfully. After stent placement, all patients could take solid food without dysphagia. Stent migration occurred in one patient and so the insertion procedure was repeated to reposition the stent. During the 3-month follow-up period after stent removal, all children could eat satisfactorily. After 6 months, 2 children required balloon dilation (3 times in one and 5 times in the other). The dysphagia score improved in all patients.

CONCLUSIONS

The use of the covered retrievable expandable stent is an effective and safe method in treating childhood corrosive esophageal stenosis.

Assessment of toxicologic interactions resulting from acute inhalation exposure to sulfuric acid and ozone mixtures

Studies examining effects of air pollutants often use single compounds, while "real world" exposures are to more than one chemical. Thus, it is necessary to assess responses following inhalation of chemical mixtures. Rabbits were exposed for 3 hr to sulfuric acid aerosol at 0, 50, 75, or 125 micrograms/m3 in conjunction with ozone at 0, 0.1, 0.3, or 0.6 ppm, following which broncho-pulmonary lavage was performed. Various pulmonary response endpoints related to general cytotoxicity and macrophage function were examined. In addition, a goal of the study was to define an improved approach to the analysis of data sets involving binary pollutant mixtures. Results were evaluated using analysis of variance with multiple linear contrasts to determine the significance of any effect in the pollutant-exposed groups compared to sham control animals and to assess the type, and extent, of any toxicological interaction between acid and ozone. Interaction was considered to occur when the effects of combined exposure were either significantly greater or less than additive. Pollutant exposures had no effect on lavage fluid levels of lactate dehydrogenase, prostaglandins E2 and F2 alpha, nor on the numbers, viability, or types of immune cells recovered by lavage. Phagocytic activity of macrophages was depressed at the two highest acid levels and at all levels of ozone. Exposure to all mixtures showed significant antagonism. Superoxide production by stimulated macrophages was depressed by acid exposure at the two highest concentrations, while ozone alone had no effect. Significant antagonistic interaction was observed following exposure to mixtures of 75 or 125 micrograms/m3 acid with 0.1 or 0.3 ppm ozone. The activity of tumor necrosis factor elicited from stimulated macrophages was depressed by acid at 75 and 125 micrograms/m3 while ozone had no effect. Exposure to mixtures of 125 micrograms/m3 acid with 0.3 or 0.6 ppm ozone resulted in synergistic interaction. This study provided additional evidence for antagonism between two common air pollutants and demonstrated that the type of interaction between sulfuric acid and ozone depended upon the endpoint but that the magnitude of any interaction was not always related to the exposure concentrations of the constituent pollutants.

Airway hyperresponsiveness in guinea pigs exposed to acid-coated ultrafine particles

Although several epidemiological studies have provided evidence that airborne sulfate particles can produce adverse health effects in susceptible individuals, there is only limited data demonstrating respiratory effects in human volunteers and experimental animals at near ambient concentrations. We have demonstrated previously that the mixing of metal oxide particles with SO2 under humid conditions produces acid-coated particles that are significantly more potent in causing pulmonary function changes than pure acid droplets. The present study examined the nonspecific airway responsiveness to acetylcholine in guinea pigs exposed to acid-coated zinc oxide particles. One and a half hours after a 1-h exposure to the aerosols or a control atmosphere, pulmonary resistance (RL) was measured in awake, spontaneously breathing animals before and during a challenge with increasing doses of iv acetylcholine (Ach). The provocative infusion rate of Ach that resulted in a 100% increase in RL (PR100) was significantly decreased (p less than .05) in animals exposed to sulfuric acid-coated metal oxide particles (approximately 30 micrograms/m3 sulfate) compared to control animals exposed to furnace gases (79.6 +/- 19.4 vs. 179.6 +/- 16.2 micrograms/kg/min, mean +/- SE, respectively). The PR100 of animals exposed to SO2 (109.1 +/- 45.4) or metal oxide particles (106.7 +/- 38.1) alone was not significantly different from that of furnace gas control animals, indicating that the acid coating on the metal oxide particles and not the particles themselves or the SO2 was responsible for the decrease in the PR100. Moreover, a 10-fold greater amount of total sulfate as a pure aqueous sulfuric acid aerosol was necessary to produce a decrease in PR100 (88.6 +/- 11.0 micrograms/kg/min) equivalent to that produced by coated particles. These results suggest that acute exposure to near-ambient concentrations of sulfuric acid under conditions that promote the formation of acid as a surface coating in respirable particles can induce a nonspecific airway hyperresponsiveness. In a similar manner, a dose-dependent significant decrease in PR100 was also produced in animals exposed to sodium sulfite droplets. Thus a single exposure to different forms of sulfur oxide aerosols can induce an alteration in the responsiveness of airway smooth muscle in the guinea pig.

The role of titratable acidity in acid aerosol-induced bronchoconstriction

We evaluated the importance of pH, titratable acidity, and specific chemical composition in acid aerosol-induced bronchoconstriction in 8 asthmatic subjects. We administered aerosols of HCl and H2SO4 at pH 2.0 in an unbuffered state and buffered with glycine. The buffered acids were given in order of increasing titratable acidity (defined as the number of ml of 1 N NaOH required to neutralize 100 ml of acid solution to pH 7.0). Each set of buffered or unbuffered acid aerosols was given on a separate day and each aerosol was inhaled through a mouthpiece during 3 min of tidal breathing. Bronchoconstriction was assessed by measurement of specific airway resistance (SRaw) before and after inhalation of each aerosol. SRaw increased by more than 50% above baseline in 1 of 8 subjects after inhalation of unbuffered HCl and in no subjects after inhalation of unbuffered H2SO4, even at pH 2.0. In contrast, SRaw increased by greater than 50% in all 8 subjects after inhalation of HCl and glycine at pH 2.0 and 7 of 8 subjects after inhalation of H2SO4 and glycine at pH 2.0. The mean titratable acidity required to increase SRaw by 50% above baseline was calculated for each challenge by linear interpolation; these values for H2SO4 and glycine (5.1 ml of 1 N NaOH) and HCl and glycine (2.2 ml of 1 N NaOH) were slightly, but significantly, different (p = 0.01) and were considerably higher than the titratable acidity of the unbuffered acids at pH 2 (1.0 ml of 1 N NaOH).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term consequences of exposure to ozone. II. Structural alterations in lung collagen of monkeys

The effects of chronic exposure to ozone on lung collagen crosslinking were investigated in two groups of juvenile cynomolgus monkeys exposed to 0.61 ppm of ozone 8 hrs per day for 1 year. One group was killed immediately after the exposure period; the second exposed group breathed filtered air for 6 months after the ozone exposure before being killed. Previous studies of these monkeys had revealed that lung collagen content was increased in both exposed groups (J.A. Last et al., (1984). Toxicol. Appl. Pharmacol. 72, 111-118). In the present study specific collagen crosslinks were quantified in order to determine whether the excess collagen in the lungs of these animals was structurally normal or abnormal. In the group killed immediately after exposure, the difunctional crosslink dehydrodihydroxylysinonorleucine (DHLNL) was elevated, as was the ratio of DHLNL to dehydrohydroxylysinonorleucine (HLNL). Lung content of the mature nonreducible crosslink hydroxypyridinium was also increased in this group. In the group killed after a 6-month postexposure period, lung content of the difunctional crosslinks DHLNL and HLNL was indistinguishable from control values. However, lung hydroxypyridinium content was significantly increased. The changes in collagen crosslinking observed in the group killed at the termination of exposure are characteristic of those seen in lung tissue in the acute stage of experimental pulmonary fibrosis. The changes seen in the postexposure group suggest that while the lung collagen being synthesized at the time the animals were killed was apparently normal, "abnormal" collagen synthesized during the period of ozone exposure was irreversibly deposited in the lungs. This study suggests that long-term exposure to relatively low levels of ozone may cause irreversible changes in lung collagen structure.

Dose-dependent effects of submicrometer sulfuric acid aerosol on particle clearance from ciliated human lung airways

We previously showed that 1 hr exposures to submicrometer sulfuric acid (H2SO4) aerosol at 100 and 1000 micrograms/m3 altered the bronchial mucociliary clearance of monodisperse 7.6 micron MMAD 99mTc-labelled ferric oxide (Fe2O3) in healthy, nonsmoking humans. The 7.6 micron particles were primarily deposited in the larger bronchial airways, where submicrometer H2SO4 has very little deposition. To determine the extent that submicrometer H2SO4 aerosol affects clearance from the more distal ciliated airways, we measured the clearance of a monodisperse 4.2 micron MMAD Fe2O3 aerosol in eight other healthy nonsmoking subjects. A greater fraction of 4.2 micron particles deposited in distal conductive airways. Bronchial mucociliary clearance was slower following 1 h nasal H2SO4 inhalations at 100, 300 and 1000 micrograms/m3 than after sham exposures, while mucociliary transport rates within the trachea and indices of respiratory mechanics were unchanged. A comparison of the effects of 1 h exposures at 100 micrograms/m3 on the clearance of 7.6 and 4.2 micron particles suggests greater physiological response in distal ciliated airways than in larger central airways.

Adaptation to alcoholic fermentation in Drosophila: a parallel selection imposed by environmental ethanol and acetic acid

Besides ethanol, acetic acid is produced in naturally fermenting sweet resources and is a significant environmental stress for fruit-breeding Drosophila populations and species. Although not related to the presence of an active alcohol dehydrogenase, adult acetic acid tolerance was found to correlate with ethanol tolerance when sensitive (Afrotropical) and resistant (European) natural populations of Drosophila melanogaster were compared. The same correlation was found when comparing various Drosophila species. Tolerance to acetic acid also correlated with the tolerance to longer aliphatic acids of three, four, or five carbons but did not correlate with the tolerance to inorganic acids (i.e., hydrochloric and sulfuric acids). These observations suggest that acetic acid is detoxified by the conversion of acetate into acetyl-CoA, a metabolic step also involved in ethanol detoxification. Future investigations on the adaptation of Drosophila to fermenting resources should consider selective effects of both ethanol and acetic acid.

Comparative effects of sulfuric and nitric acid rain on litter decomposition and soil microbial community in subtropical plantation of Yangtze River Delta region

Acid rain is mainly caused by dissolution of sulfur dioxide and nitrogen oxides in the atmosphere, and has a significant negative effect on ecosystems. The relative composition of acid rain is changing gradually from sulfuric acid rain (SAR) to nitric acid rain (NAR) with the rapidly growing amount of nitrogen deposition. In this study, we investigated the impact of simulated SAR and NAR on litter decomposition and the soil microbial community over four seasons since March 2015. Results first showed that the effects of acid rain on litter decomposition and soil microbial were positive in the early period of the experiment, except for SAR on soil microbes. Second, soil pH with NAR decreased more rapidly with the amount of acid rain increased in summer than with SAR treatments. Only strongly acid rain (both SAR and NAR) was capable of depressing litter decomposition and its inhibitory effect was stronger on leaf than on fine root litter. Meanwhile, NAR had a higher inhibitory effect on litter decomposition than SAR. Third, in summer, autumn and winter, PLFAs were negatively impacted by the increased acidity level resulting from both SAR and NAR. However, higher acidity level of NAR (pH=2.5) had the strongest inhibitory impact on soil microbial activity, especially in summer. In addition, Gram-negative bacteria (cy19:0) and fungi (18:1ω9) were more sensitive to both SAR and NAR, and actinomycetes was more sensitive to SAR intensity. Finally, soil total carbon, total nitrogen and pH were the most important soil property factors affecting soil microbial activity, and high microbial indices (fungi/bacteria) with high soil pH. Our results suggest that the ratio of SO₄^2- to NO₃^- in acid rain is an important factor which could affect litter decomposition and soil microbial in subtropical forest of China.

Induction of kinetochore positive and negative micronuclei in V79 cells by the alkylating agent diethylsulphate

The induction by diethylsulphate of micronuclei derived from acentric fragments or from whole chromosomes was studied in Chinese hamster V79 cells using autoantibodies from the serum of a scleroderma patient (CREST-syndrome) to detect centromere--kinetochore structures. Centromere-containing micronuclei appeared early after treatment and plateaued both earlier and at lower level than centromere-lacking micronuclei. The frequency of centromere-containing micronuclei was in good agreement with that of mitotic chromosome displacement, suggesting that a high proportion of displaced chromosomes were transmitted to the cytoplasm of one of the two daughter cells, where they gave rise to micronuclei. On the contrary, centromere-lacking micronuclei were more frequent than what could be expected from chromosome fragments observed in mitotic stages.

Furnace-generated acid aerosols: speciation and pulmonary effects

Guinea pigs were exposed to ultrafine aerosols (less than 0.1 micron) of zinc oxide with a surface layer of sulfuric acid. These acid-coated aerosols are typical of primary emissions from smelters and coal combustors. Repeated daily 3-hr exposures for 5 days produce decrements in lung volumes and pulmonary diffusing capacity and elevations of lung weight/body weight ratio, protein, and number of neutrophils in pulmonary lavage fluid at concentrations of 20 micrograms/m3. A single 1-hr exposure to 20 micrograms/m3 causes increased bronchial reactivity. Higher concentrations of conventionally generated sulfuric acid mist are required to produce responses of similar magnitude.

Response of the bronchial mucociliary clearance system in rabbits to inhaled sulfite and sulfuric acid aerosols

A group of eight rabbits was exposed (orally) for 1 hr to a distilled water aerosol (sham control) or to submicrometer aerosols of either a transition metal sulfite complex (Fe(III)-S(IV], sodium sulfite (Na2SO3), or sulfuric acid (H2SO4). Mucociliary clearance was evaluated by external retention measurements of radioactively tagged tracer particles from the bronchial tree. Fe(III)-S(IV) in the range of 238 to 1227 micrograms/m3 (as SO2-3) produced no significant change from sham control in the mean residence time (MRT) of the tracer, indicating no effect upon mucociliary clearance rate. On the other hand, Na2SO3 at levels greater than or equal to 1200 micrograms/m3 (as SO2-3) resulted in clearance acceleration; the lack of effect of Fe(III)-S(IV) is possibly due to its stability. H2SO4 at 260 to 2155 micrograms/m3 produced a significant dose-related response, indicating clearance acceleration at low concentrations and a depression at higher levels.

Effects in rats and guinea pigs of short-term exposures to sulfuric acid mist, ozone, and their combination

Ozone and the oxides of sulfur are common environmental pollutants. The acute pulmonary lesions caused by ozone and sulfuric acid mist in rats and guinea pigs have been characterized. Rats are not affected by sulfuric acid mist in concentrations up to 100 mg/m3 except for reduced body weight at the higher doses. A true alveolitis develops in guinea pigs exposed to more than 20 mg/m3 sulfuric acid mist. The ozone lesion is primarily confined to the terminal bronchioles and proximal alveoli. In combination studies with up to 2 ppm ozone and up to 10 mg/m3 sulfuric acid mist, the pulmonary lesion and lung/body weight data were essentially the same as in exposure to ozone alone, and the number of statistically significant synergistic effects in rats and guinea pigs was about what one would expect to observe by chance alone.

Synergistic action of cord factor and mycobacterial sulfatides on mitochondria

The mechanism of a synergistic toxicity of 6,6'-dimycoloyl-alpha,alpha'-d-trehalose (cord factor) and 2,3,6,6'-tetraacyl-alpha,alpha'-d-trehalose 2'-sulfate (sulfolipid I) for mice was studied. Sulfolipid I was entirely nontoxic, but it markedly accelerated the lethal toxicity of cord factor for mice. In vivo, sulfolipid I affected neither respiration nor accompanying phosphorylation of mouse liver mitochondria, whereas in vitro, it induced a swelling and disruption of mitochondrial membranes and strongly inhibited mitochondrial oxidative phosphorylation. The effect of sulfolipid I on mitochondrial structure and function in vitro was neutralized by bovine serum albumin and various animal sera, whereas that of cord factor and cord factor plus sulfolipid I was not prevented by bovine serum albumin. The simultaneous injection of cord factor and sulfolipid I caused an intensive fragmentation of mitochondria and a marked decrease in respiratory and phosphorylative activity in mitochondria. These data indicate that sulfolipid I can achieve an effective attack on mitochondria in combination with cord factor in vivo and induces heavier damage in mitochondrial structure and function than that produced by cord factor alone.

Health effects of acid aerosols formed by atmospheric mixtures

Under ambient conditions, sulfur and nitrogen oxides can react with photochemical products and airborne particles to form acidic vapors and aerosols. Inhalation toxicological studies were conducted, exposing laboratory animals, at rest and during exercise, to multicomponent atmospheric mixtures under conditions favorable to the formation of acidic reaction products. Effects of acid and ozone mixtures on early and late clearance of insoluble radioactive particles in the lungs of rats appeared to be dominated by the oxidant component (i.e., the mixture did cause effects that were significantly different from those of ozone alone). Histopathological evaluations showed that sulfuric acid particles alone did not cause inflammatory responses in centriacinar units of rat lung parenchyma (expressed in terms of percent lesion area) but did cause significant damage (cell killing followed by a wave of cell replication) in nasal respiratory epithelium, as measured by uptake of tritiated thymidine in the DNA of replicating cells. Mixtures of ozone and nitrogen dioxide, which form nitric acid, caused significant inflammatory responses in lung parenchyma (in excess of effects seen in rats exposed to ozone alone), but did not damage nasal epithelium. Mixtures containing acidic sulfate particles, ozone, and nitrogen dioxide damaged both lung parenchyma and nasal epithelia. In rats exposed at rest, the response of the lung appeared to be dominated by the oxidant gas-phase components, while responses in the nose were dominated by the acidic particles. In rats exposed at exercise, however, mixtures of ozone and sulfuric acid particles significantly (2.5-fold) elevated the degree of lung lesion formation over that seen in rats exposed to ozone alone under an identical exercise protocol.

Effects of fine and ultrafine sulfuric acid aerosols in guinea pigs: alterations in alveolar macrophage function and intracellular pH

Acidic sulfate is the most toxicologically important sulfur oxide which exists in the ambient air. To determine if particle size influences toxic effects of sulfuric acid, we investigated the effects of sulfuric acid aerosols of two different sizes on biochemical and cellular parameters of bronchoalveolar lavage fluid from exposed guinea pigs. Guinea pigs were exposed to fine (mass median diameter, 0.3 micron), and ultrafine (mass median diameter, 0.04 micron) sulfuric acid aerosols at 300 micrograms/m3 for 3 hr/day. The animals were euthanized immediately and 24 hr after 1 and 4 days of exposure and lungs were lavaged. Elevated beta-glucuronidase, lactate dehydrogenase activities, and total protein concentration as well as decreased cell viability were observed in the lavage after a single exposure to sulfuric acid aerosols of both sizes. These alterations were small, though statistically significant, and transient. No alteration in these parameters was observed after 4 days of exposure to acid aerosols. In contrast, sulfuric acid-induced alterations in alveolar macrophage function were more pronounced and longer lasting. Immediately after a single exposure to fine acid, there was a 2.7-fold increase in the spontaneous tumor necrosis factor (TNF) release over that in the control group while endotoxin-stimulated TNF release was increased by 2.2-fold. In addition, acid aerosols of both sizes increased the TNF release from macrophages after 4 days of exposure, although there was no clear temporal pattern of induction or recovery. Furthermore, immediately after 4 days of exposure to either fine or ultrafine acid, the amount of H2O2 that could be induced from baseline production by alveolar macrophages was 2.2-fold higher than that of the controls. The phagocytic function of macrophages was also altered by exposure to sulfuric acid aerosols. Twenty-four hours after single or multiple exposure, fine acid enhanced (as high as 78% above control) the in vitro phagocytic activity of alveolar macrophages while ultrafine acid depressed the phagocytic capacity (as much as 50% below that in the control). In addition to these biochemical parameters and cellular functions, we also measured the intracellular pH (pHi) of macrophages harvested after exposures to these acid aerosols using a pH-sensitive fluorescent dye. The resting pHi was depressed after a single exposure to both acid aerosols. The depression in pHi persisted 24 hr after ultrafine acid exposure.(ABSTRACT TRUNCATED AT 400 WORDS)