Increase in metallothionein produced by chemicals that induce oxidative stress

Metallothionein (MT) is a low-molecular-weight protein with a high cysteine content that has been proposed to play a role in protecting against oxidative stress. For example, MT has been shown to be a scavenger of hydroxyl radicals in vitro, and cells with high levels of MT are resistant to radiation. However, it is not known if compounds that cause oxidative stress affect MT levels. Therefore, mice were injected subcutaneously with 11 chemicals (t-butyl hydroperoxide, paraquat, diquat, menadione, metronidazole, adriamycin, 3-methylindole, cisplatin, diamide, diethyl maleate, and phorone) that produce oxidative stress by four main mechanisms. MT was quantitated in the cytosol of major organs (liver, pancreas, spleen, kidney, intestine, heart, and lung) by the Cd/hemoglobin radioassay 24 hr after administration of the chemicals. All agents significantly increased MT levels in at least one organ. Liver was the most responsive to these agents in that all 11 chemicals increased MT concentrations in liver, with diethyl maleate, paraquat, and diamide producing 20- to 30-fold increases. Pancreas and kidney were the next most responsive organs to these chemicals. The organ least responsive to these agents was the heart, as only 3 compounds caused significant increases in MT concentrations in heart. Diethyl maleate and diquat were the most general inducers of MT in that they increased MT in six of the seven organs examined. No treatment resulted in a significant decrease in MT concentration in any organ. In conclusion, chemicals that produce oxidative stress by one of four distinct mechanisms are very effective at increasing MT concentrations in a variety of organs. This suggests that MT might be involved in protecting against oxidative stress.

Bioactivation of 3-methylindole by isolated rabbit lung cells

3-Methylindole (3MI) is a pneumotoxin that causes selective lung lesions indicative of Clara cell and alveolar epithelial cell damage in ruminants and rodents. The present study examined the cytotoxicity of 3MI to isolated rabbit Clara cells, type II alveolar epithelial cells, and alveolar macrophages. 3MI produced a dose-dependent cytotoxicity to Clara cells detectable within 1 hr of incubation at 37 degrees C which reached a maximum at 3 hr. Concentrations of 0.25 and 0.5 mM 3MI were cytotoxic to Clara cells, while type II and alveolar macrophages required 1 mM 3MI before cytotoxicity was observed. The cytochrome P450 suicide substrate inhibitor, 1-aminobenzotriazole, inhibited 3MI-induced cytotoxicity in Clara cells, type II cells, and alveolar macrophages. These observations were consistent with a cytochrome P450-mediated bioactivation of 3MI to a toxic intermediate. Studies with a trideuteromethyl analog of 3MI demonstrated a much reduced cytotoxicity to Clara cells as well as to type II cells, and macrophages. The deuterium isotope effect suggested that C-H bond breakage at the 3-methyl group is a requisite oxidative transformation in the bioactivation of 3MI to a selective lung cell cytotoxin. The selectivity of cellular cytotoxicity is probably associated with higher rates of bioactivation by Clara cell cytochrome P450 monooxygenases compared to those of type II cells and macrophages. These studies demonstrate that 3MI is bioactivated in isolated pulmonary cells without the intervention of other organs and that bioactivation requires functional cytochrome P450 enzymes.

Interaction of two complementary fragments of the bovine spinal cord myelin basic protein with phospholipid bilayers. An ESR spin-label study

The myelin basic protein (MBP) from bovine spinal cord was cleaved at the single tryptophan residue to produce an N-terminal fragment (F1) of molecular weight 12.6K and a C-terminal fragment (F2) of molecular weight 5.8K. The interactions of the two fragments with bilayers of the acidic lipid dimyristoylphosphatidylglycerol (DMPG) were compared with those of the intact protein, by using both chemical binding assays and spin-label electron spin resonance spectroscopy. The saturation binding stoichiometries of the two fragments were found to sum to that of the MBP, having values of 11, 24, and 36 mol of DMPG/mol of protein for F2, F1, and the MBP, respectively. The strength of binding was found to increase in the order F2 less than F1 less than MBP, which follows that of the net charges on the different fragments. The ionic strength dependence of the protein binding indicated that the interaction is primarily of electrostatic origin. The efficiency of displacement of the proteins by salt was in the order F2 greater than F1 greater than MBP, which correlates with both the strength of binding and the net charge on the different protein fragments. Nitroxide derivatives of phosphatidylglycerol (PG) labeled on the sn-2 chain were used to probe the protein-induced changes in the acyl chain dynamics. Both the fragments and the MBP decreased the lipid chain mobility as recorded by the C-5 atom and C-12 atom position nitroxide-PG spin-labels, in a manner which followed the protein binding curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Complete amino acid sequence of canine miniplasminogen

The complete amino acid sequence of canine miniplasminogen (Mr 36,678, 333 residues) was determined with the aid of fragments obtained by cleavage with BNPS-skatole, cyanogen bromide or clostripain. The fragments were aligned with overlapping sequences. Sequence comparison with miniplasminogens of other species gave identities in the range of 80% (bovine) and 88% (human), indicating the presence of the same structural and functional domains as in the other species. Sequence comparison of different miniplasminogens showed that plasminogens of species activated by streptokinase have identical residues in positions 49, 83 and 161 of the plasmin light chain. The triad of these amino acids may represent at least one of eventually several prerequisites for the interaction and activation of plasminogen with streptokinase.

Effect of 3-methylindole on the plasma and lung concentrations of prostaglandins and thromboxane B2 in goats

1. The role of prostanoids in 3-methylindole (3MI)-induced lung disease was investigated. Goats were infused with 3MI in propylene glycol at a dose of 35 mg 3MI/kg body weight. Control goats were infused with propylene glycol alone. 2. Blood was collected at regular intervals starting 24 hr before and ending 72 hr following 3MI infusion. In a second experiment, 3MI-treated goats were killed at 2, 6, 12, 24, 48 and 72 hr post-infusion. The concentrations of PGF2 alpha, PGE, 6-keto PGF1 alpha and TXB2 in plasma and lung of 3MI-infused and control goats were determined by radioimmunoassay. 3. Comparison of individual prostanoid concentrations showed that 3MI-infused and control goats exhibited similar plasma profiles for all four prostanoids measured. 4. In addition, prostanoid concentrations in lungs did not seem to be affected by 3MI infusion. 5. Thus, plasma and lung prostaglandin and TXB2 concentrations do not appear to be altered in 3MI-induced lung disease.

Zinc suppression of free radicals induced in cultures of rat hepatocytes by iron, t-butyl hydroperoxide, and 3-methylindole

The effect of zinc on lipid peroxidation initiated by either ferric-nitrilotriacetate, t-butyl hydroperoxide, or 3-methylindole was studied using primary monolayer cultures of rat liver parenchymal cells. The malondialdehyde content of the cells and culture medium was used to estimate the extent of lipid peroxidation. As the zinc concentration of the culture medium was increased from 1 to 48 microM, peroxidation was diminished. Cellular zinc and metallothionein levels were proportionally increased by supplemental zinc. Zinc supplementation of the medium inhibited NADPH-cytochrome c reductase activity and stimulated glutathione peroxidase activity. The uptake of iron into the hepatocytes was significantly reduced as the level of zinc was raised, suggesting that zinc antagonizes uptake of chelated iron into isolated hepatocytes and in this way blocks iron-induced peroxidation. Furthermore, induction of metallothionein synthesis by zinc may contribute to the reduction in free radicals. Spectra from electron spin resonance studies, using phenylbutylnitrone as a spin-trapping reagent, demonstrated that free radical production was inversely related to the zinc concentration of the culture medium. Spin trap data suggest that metallothionein added to lysed cells in vitro decreases free radical production. Studies using the spin trap, 3,3,5,5-tetramethylpyrroline-N-oxide indicated that cumulatively the predominant radical present in the cultures was a phenyl radical with hydroperoxide or methylindole. Collectively, our data demonstrate that zinc inhibits free radical production and lipid peroxidation in cultured hepatocytes. The mode of action of zinc could occur via free radical scavenging by zinc-induced metallothionein and/or by processes related to cytochrome P-450 and glutathione peroxidase, since these were also found to be sensitive to zinc supplementation levels of the culture medium.

The effect of 3-methylindole on the quantity and functional quality of lung surfactant

Acute bovine pulmonary edema is a naturally occurring lung disease caused by 3-methylindole (3MI), a ruminal fermentation product of tryptophan. Morphological and in vitro studies have suggested that 3MI causes abnormalities in phospholipid synthesis. The present study was designed to investigate the effect of 3MI on the quantity and functional quality of surfactant using the goat as an experimental model. Following intravenous infusion of 3MI, goats were killed at 6-, 18-, and 30-h intervals. The lungs were removed and intracellular surfactant, in the form of lamellar bodies, and extracellular surfactant from alveolar lavage were quantified. 3MI treatment did cause modest changes in the lamellar body phospholipid pools, decreasing the quantity of phosphatidylcholine and the proportion of palmitate in this fraction. The quantity of lavage phospholipids was not significantly affected. There was an increase in the protein content of the lavage, reflecting the presence of edema. The functional quality of the surfactant isolated from the lavage fraction was tested in vitro using a pulsating bubble surfactometer. 3MI infusion decreased the ability of surfactant to lower the surface tension of an air bubble at maximum radius and during compression.

3-Methylindole inhibits lipid peroxidation

The mechanism of pneumotoxicity of 3-methylindole has been postulated to occur via protein alkylation or lipid peroxidation. This report describes the effects of the addition of 3-methylindole to goat lung microsomes to evaluate the possibility that this xenobiotic may increase NADPH-supported lipid peroxidation. Concentrations of malondialdehyde were measured as an index of lipid peroxidation. Instead of a stimulation of lipid peroxidation by 3-methylindole, a complete inhibition of lipid peroxidation was produced by concentrations of 3-methylindole as low as 10 microM. The addition of 3-methylindole to actively peroxidizing microsomes (NADPH-supported) caused an immediate cessation of malondialdehyde production. These results demonstrate that 3-methylindole pneumotoxicity does not proceed by a mechanism of lipid peroxidation, but in fact, this molecule may act as an effective antioxidant to prevent lipid peroxidation in pulmonary tissue.

The effect of 3-methylindole on the rates of phospholipid and neutral lipid synthesis in cultured fibroblasts

The present study was designed to test the hypothesis that a pneumotoxin, 3-methylindole, alters the basic metabolic pathways involved in phospholipid and neutral lipid synthesis in cultured fibroblasts. Rat skin fibroblasts were obtained from day-old pups. Confluent monolayers were preincubated for up to 24 h with a range of concentrations (0-0.76 mM) of 3-methylindole. Following these treatments, the cell lipids were labelled by incubation for 6 h with [14C]glycerol. The lipids were extracted, separated by thin layer chromatography, and the radioactivity in each fraction was determined. 3-Methylindole had no effect on the total incorporation of [14C]glycerol into lipids, but significantly altered the distribution among lipid fractions. Incubation with 3-methylindole caused a decrease in the incorporation of [14C]glycerol into phosphatidylcholine, while radioactivity accumulated in the neutral lipid fraction. The other lipid fractions responded variably. Similarily, Flow 2000 human diploid lung fibroblasts were incubated for 24 h with 3-methylindole followed by treatment with [14C]glycerol, resulting in a 74% decrease in the incorporation of [14C]glycerol into phosphatidylcholine and a 50% increase in its accumulation in neutral lipid. The results indicate that 3-methylindole inhibits the synthesis of phosphatidylcholine from diacylglycerol precursors on the endoplasmic reticulum in cultured fibroblasts. This is an important observation as it shows that 3-methylindole affects the synthesis of phospholipids required for membrane turnover in cells that are not specialized for the production of phospholipids for surfactant.

A comparison of the dodecyl sulfate-induced precipitation of the myelin basic protein with other water-soluble proteins

The interactions of sodium dodecyl sulfate with a number of proteins were examined at a variety of pH values ranging from 4.8 to 11.6. The dodecyl sulfate-induced precipitation of some of these proteins was observed within a relatively limited range of total dodecyl sulfate concentration. Most of the basic proteins precipitated at low pH but as the isoelectric point of the protein was approached the amount of protein that precipitated decreased. Bovine myelin basic protein was unique in that it precipitated at all pH values examined both above and below its isoelectric point. Thus, the dodecyl sulfate-induced precipitation of myelin basic protein appears to be different from the dodecyl sulfate-induced precipitation of most proteins. A comparison of protein precipitation at equivalent dodecyl sulfate:protein molar or weight ratios revealed very little difference in the precipitation behavior of the proteins studied. When the bovine myelin basic protein was cleaved at its single tryptophan residue, the N-terminal fragment (1-115) formed insoluble dodecyl sulfate complexes at pH values ranging from 4.8 to 9.2. The C-terminal fragment (116-169) precipitated almost completely at pH 4.8 but to a lesser extent at pH 7.4 and 9.2. Equimolar mixtures of the N- and C-terminal fragments precipitated in the presence of dodecyl sulfate at pH 7.4 and 9.2 to an extent greater than the C-terminal fragment alone but comparable to the N-terminal fragment alone or the whole basic protein. These results suggest: that the mechanism by which dodecyl sulfate induces the precipitation of myelin basic protein may be unique compared to other proteins and that the intact myelin basic protein is not necessary for its precipitation by dodecyl sulfate.

The amino-acid sequence of the variable region of a carbohydrate-containing amyloid fibril protein EPS (immunoglobulin light chain, type lambda)

The amino-acid sequence of the variable region of a carbohydrate-containing amyloid fibril protein EPS of immunoglobulin lambda light chain origin has been elucidated. The protein was isolated from the liver of a patient (EPS) with an immunocyte dyscrasia of the IgM type. The molecular mass of this protein was found to be about 20 kDa including an oligosaccharide chain linked to it. The amino-acid sequence determination involved automatic Edman degradation of polypeptides obtained after cleaving the protein with BNPS-skatole, trypsin and thermolysin. The proposed sequence of the variable region of the protein showed that it may be assigned to the V lambda I subgroup. A tryptic and a thermolysinolytic peptide both containing the carbohydrate were isolated and characterized, and the localization of an oligosaccharide chain linked to asparagine was established.

Infrared spectra of carbon monoxide complexes of indoleamine 2,3-dioxygenase and L-tryptophan 2,3-dioxygenases. Effects of substrates on the CO-stretching frequencies

Carbonmonoxy indoleamine 2,3-dioxygenase from rabbit small intestine exhibited two CO stretch bands at 1953 and 1933 cm-1 with half-band widths (delta v 1/2) of both approximately 15 cm-1. Upon addition of an excess amount of L-tryptophan, the substrate, the spectrum changed into that with an intense single band at 1902 cm-1 with the delta v 1/2 of 15 cm-1. Carbonmonoxy L-tryptophan 2,3-dioxygenase of Pseudomonas acidovorans in the absence of L-tryptophan showed a fused CO stretch band which consists of two components at 1965 and 1958 cm-1 (delta v 1/2 for the fused band; 25 cm-1), which was converted into a sharp single band at 1968 cm-1 (delta v 1/2; 10 cm-1) upon addition of excess L-tryptophan. On the other hand, CO complex of rat liver L-tryptophan 2,3-dioxygenase in the absence of L-tryptophan gave a spectrum with a poorly defined peak around 1961 cm-1. By the addition of L-tryptophan, the spectrum changed into that with two distinct bands at 1972 and 1920 cm-1 (delta v 1/2; 6 and 13 cm-1, respectively). These spectra were insensitive to pH in a range where the enzymes were not denatured (neutral to near pH 9). The infrared spectra of the carbonmonoxy enzymes were also affected by the addition of certain effectors such as skatole and alpha-methyl-DL-tryptophan, which facilitate the binding of L-tryptophan to the catalytic site of intestinal and Pseudomonas enzymes, respectively. However, the changes were of different types from those by the saturating amount of L-tryptophan. Possible mechanisms for these phenomena are discussed in relation to the structure of the heme-CO complex in these heme-containing dioxygenases.

The effect of 3-methylindole on the uptake and incorporation of 14C-choline into phospholipids in lung tissue slices

3-Methylindole (3MI) is the causative agent in the development of acute bovine pulmonary edema. Microscopic studies revealed a structural disruption in the lamellar bodies of type II cells, indicating an abnormal metabolism of phospholipid in the lung of 3MI treated animals. In the present study, lung slices from 4 goats were used to investigate the changes in phosphatidylcholine metabolism induced by 3MI. Eighteen slices were cut from each healthy lung and divided into control and 3MI groups. After a 4-hr pretreatment with 3MI (.19 or .57 mM) or carrier, the level of incorporation of 14C-choline into phosphatidylcholine, sphingomyelin and their water soluble intermediates was studied. The uptake of 14C-choline and its incorporation into phosphatidylcholine and sphingomyelin was depressed by 3MI treatment. In the water soluble fractions, the radioactivity increased in free choline and CDP-choline, while it decreased in P-choline. This suggests that choline kinase and the P-choline transferases have become relatively more rate limiting and may play a role in the depressed de novo synthesis of phosphatidylcholine induced by 3MI.

Ultrastructure of bronchopulmonary lavage cells from bovines administered 3-methylindole. I. 12 hours post-treatment

Ultrastructure of the bronchopulmonary lavage cells, viz., pulmonary alveolar macrophages (AM), neutrophils, plasma cells, ciliated epithelial cells and lymphocytes from calves 12 h following 3-methylindole (3-MI) ingestion is documented in this study. The AM had increased in number and size, and appeared stimulated as indicated by an elevated number of phagosomes and/or various combinations of structures resembling phagolysosomes. Pseudopodia on majority of the neutrophils were either sparse or absent. Morphologic parameters of heightened secretion were present in the occasionally noticed plasma cells. Ciliated epithelial cells which were only sometimes seen contained necrotic mitochondria. Lymphocytes were rarely encountered and were unaltered by the treatment. Ultrastructure of the bronchopulmonary lavage cells from the 3-MI-exposed calves demonstrates cellular response to the respiratory conditions induced by the chemical.

Effect of energy or protein supplements containing monensin on ruminal 3-methylindole formation in pastured cattle

The metabolism of 3-methylindole (3MI), a ruminal degradation product of L-tryptophan, results in acute bovine pulmonary edema and emphysema. The effect of feeding an energy or protein supplement containing monensin on ruminal 3MI formation in pastured beef cattle was investigated. A luxuriant pasture of orchard grass was established in a field that was seeded 1 year before the start of the grazing period. This 4-ha pasture was cut, fertilized, divided into 2 equal plots, and then irrigated during a 22-day growth period. All cows were fed a restricted quantity of low-quality alfalfa hay for 33 days before the grazing period. Two experiments were conducted, using 38 cows (30 of the cows were used in experiment I and all 38 cows were used in experiment II). Cows in each experiment were randomly allotted to 2 groups. One group was designated in each experiment as the control group. The control group for experiment I was fed an energy supplement. The control group for experiment II was fed a protein supplement. The 2nd group in each experiment was given the same supplement as the respective control group with 200 mg of monensin added/! kg of feed. Supplements were fed on days - 1, 0, 1, 2, 3, 4, 5, 6, and 7 of each experimental period. Supplements were fed twice daily to provide 1 kg of supplement/cow. Cows were given access to orchard grass pasture on day 0 of each experiment. Ruminal fluid was collected daily for analysis of 3MI, indole, and volatile fatty acids. Ruminal fluid pH was recorded immediately after collection. Ruminal pH of all cows decreased from 7.3 to 6.2 during the first few days of grazing the orchard grass. Ruminal pH then gradually increased toward neutrality by experimental day 10. Significantly (P < 0.01) higher molar percentages of pro-pionate and lower (P < 0.01) molar percentages of acetate and butyrate were observed in the 2 groups fed the supplements with added monensin. These changes in propionate and acetate remained different (P < 0.01) from those of the controls for 10 days (or 3 days after the last monensin feeding). Compared with pregrazing ruminal concentrations of 3MI, the 3MI values were elevated (P < 0.01) by day 1 in all groups, except in the monensin-treated cows of experiment I. In experiment I, 3MI concentrations were highest on experimental days 5 and 10 in control and monensin-treated cows, respectively. In experiment II, 3MI concentrations peaked on day 4 for the control cows and day 6 for the monensin-treated cows. Monensin supplementation reduced (P < 0.05) 3MI formation on days 1 through 5 in experiment I and on days 1 through 3 in experiment II. Formation of 3MI was increased in ruminal fluid of all cows after an abrupt change to the pasture forage, but the rate of 3MI production was slower, and a lower peak concentration of 3MI was reached in cows fed monensin than was observed in the controls. These results indicate that monensin administration in either an energy or protein supplement effectively reduced ruminal 3MI formation in pasture-fed cattle.

The effect of 3-methylindole on phospholipid synthesis in goat lung tissue slices

3-Methylindole (3MI), a ruminal fermentation product of tryptophan, is the causative agent in the development of acute bovine pulmonary edema (ABPE). The disease is dependent on the activation of 3MI by mixed function oxidases (MFO). Electron micrographs have revealed that the lamellar bodies of the type II cells are disrupted in structure and contain neutral lipids (NL) instead of surfactant phospholipids (PL). Goat lung slices were used to investigate the changes in PL metabolism induced by 3MI. Eighteen slices were cut from each lung and divided into control, 3MI (0.57 mM), and indole (0.57 mM) groups. After a 3-hr pretreatment with these compounds, the slices were incubated with [14C]acetate. The lipids were extracted and separated. 3MI inhibited the incorporation of [14C]acetate into all of the PL studied, but had little effect on its incorporation into NL. Indole displays the same effects on membranes as 3MI, but is not activated by the MFO system and does not induce lung injury. Indole pretreatment had little effect on acetate incorporation in any of the lipid fractions. These results indicate that metabolism of 3MI in lung slices is responsible for the depression of PL synthesis in vitro. Increasing the level of unlabeled choline in the medium from 10 microM to 10 microM had no effect on the depression of [14C]acetate incorporation into phosphatidylcholine (PC). This suggests that choline uptake is not limiting the synthesis of PC in the 3MI-treated lung slices.

Failure of 3-methylindole to contract the bovine pulmonary vein or to release mediators of anaphylaxis from the bovine lung in vitro

Strips of smooth muscle from the pulmonary vein, pulmonary artery, trachea and bronchus of calves were incubated in an organ bath with 3-methylindole (3MI) and 3-methyloxindole (3MOI). 3MI and 3MOI (5-640 micrograms/ml) did not cause contraction of any of the isolated smooth muscle preparations. No evidence for the release of mediators of anaphylaxis was obtained when chopped bovine lung preparations were incubated with 3MI (20 micrograms/ml) and 3MOI (25 micrograms/ml). Results of the present work diminish the possibility that the pneumotoxic effect of 3MI is due to a primary hydrodynamic imbalance across the alveolocapillary membrane resulting in excess filtration over reabsorption.

Some effects of indole on the interaction of amino acids with tryptophanase

Although indole is a potent inhibitor (KI = 0.01 mM) of pyruvate formation from substrates of tryptophanase (EC 4.1.99.1, from Escherichia coli), we could not detect binding of indole to free tryptophanase (KD greater than 1.0 mM). However, indole, skatole, and toluene increased the affinity of tryptophanase for certain inhibitory amino acids. Binding of amino acids with small side chains (e.g. Ala, Gly) was increased, but there was little or no effect on the binding of amino acids with bulky side chains (e.g. norvaline, ethionine). These effects were quantitated by using changes in the absorption spectra of the enzyme . amino acid complexes. Indole decreases the absorbance obtainable at 500 nm for amino acids with small hydrophobic side chains (L-Ala, Gly), increases this absorbance for amino acids with small polar side chains (beta-cyano-L-alanine), and does not change the spectra of tryptophanase complexes with amino acids with bulky side chains, i.e. amino acids whose binding affinities are unaffected by indole. These spectral differences are interpreted in terms of an effect of bound indole (or side chain binding) on the partitioning of the bound amino acid between catalytic forms of the enzyme. The data indicate that substrate-induced conformational changes occur at the enzyme active site that generate a high affinity indole-binding site during catalytic turnover of tryptophanase and are important in the catalytic functioning of the enzyme. These changes also explain reproducible differences in KI values observed previously for amino acids in different assay systems used for steady state kinetic inhibition studies. The optimal conditions for the growth of E. coli for tryptophanase production are outlined, together with a procedure for purification of holotryptophanase.

Pathophysiologic studies of calves given 3-methylindole intraruminally

Intraruminal administration of 0.25 g of 3-methylindole (3MI; skatole/kg of body weight) to seven young calves generally caused mild respiratory signs and lesions, accompanied by only slight changes in cardiopulmonary function. Moderate depression, trembling, and irregular respiratory rate were observed between postadministration hours (PAH) 6 and 12. By PAH 24 at this dosage, abnormal clinical signs were not present. Statistically significant (P less than or equal to 0.05) changes observed in blood gas data from the seven calves were a decrease in aortic oxygen tension at PAH 12, increases in free-flowing venous oxygen tension in the intervals between PAH 6 and 12 and between PAH 6 and 24, and an increase in occluded venous oxygen tension at PAH 24. All calves had increases (although generally not statistically significant) in heart rate, cardiac output, cardiac index, stroke volume, and stroke index after 3MI administration. Mean aortic and pulmonary arterial pressure changes were generally small and variable. At necropsy, the lungs of the calves did not collapse when the thorax was opened. Patchy areas of consolidation (0.5 cm in diameter) were scattered throughout the parenchyma. Pulmonary edema or emphysema was not observed grossly. Microscopically, the alveolar septae were irregularly thickened because of edema, infiltration by polymorphonuclear and mononuclear cells, and vascular congestion. Interstitial lesions were patchy in distribution and severity and corresponded to the areas of consolidation observed grossly. Alveolar epithelial hypertrophy and hyperplasia were present, and an occasional focus of alevoli contained fluid of edema. Degeneration of individual hepatocytes was observed in scattered areas of the liver, especially in the periportal areas. It was concluded that differences in 3MI dosage response may exist between young calves and adult cattle in which calves are more resistant to the pulmonary cytotoxicity of 3MI.

3-methylindole-induced pulmonary injury in goats

Ruminal administration of 3-methylindole in goats severe pulmonary edema and respiratory distress. Electron microscopic studies of lungs reveal extensive degeneration and necrosis of alveolar membranous pneumocytes and bronchiolar epithelium. The necrosis of the pneumocytes is followed by proliferation of granular pneumocytes, which repopulate the alveolar basal lamina scaffold. 3-Methylindole may also induce proliferation of smooth endoplasmic reticulum in the remaining membranous pneumocytes and nonciliated columnar cells, indicating that these two cell types are involved in the xenobiotic function of the lung. The results suggest that 3-methylindole in cigarette smoke may play an important role in the pathogenesis of small airway disease and emphysema, and that patients with severe liver diseases or portocaval shunt may be predisposed to diffuse alveolar damage by 3-methylindole produced in the intestinal tract.