Hanspeter Witschi

In vivo oxidation of reduced nicotinamide-adenine dinucleotide phosphate by paraquat and diquat in rat lung

Intravenous injection of rats with 156 mumol/kg of paraquat or 140 mumol/kg of diquat produced, within 60 min, a sharp drop in the ratios of NADPH to NADP in lung. The effect persisted for a time period of at least 24 h. Exposure to 100% oxygen enhanced the toxicity of both compounds without substantially amplifying changes in the NADPH/NADP ratio. Lungs retained the capability to synthesize adenine nucleotides de novo. Electron microscopic studies showed that both paraquat and diquat damage type I alveolar cells, but only paraquat produces type II cell lesions. Although bipyridylium herbicides produce acute oxidation of NADPH in vivo, there seems not to exist a straightforward relationship between this event and cell damage.

Electron microscopy of butylated hydroxytoluene-induced lung damage in mice

Abstract This study was undertaken to analyze systematically the ultrastructural changes of the alveolar cells at several time intervals from 6 hr to 9 days following a single intraperitoneal injection (400 mg/kg) of butylated hydroxytoluene (BHT). Observation of the lung in treated mice showed ultrastructural changes in all septal cells in several focal areas. The sequence of events observed was as follows: (a) Type I epithelium was first to be damaged. From Day 1 to Day 3, this cell type exhibited alteration of cytoplasmic organelles, breaks in the plasmalemma, and a complete destruction on Days 2 and 3, leaving the basal lamina and the capillary endothelium intact. (b) After type I cells had been damaged, type II epithelium started to divide and transform themselves as early as Day 2 into a cell resembling type I in order to replace the original type I epithelium. This new cell changed its shape to become squamous, eliminated lamellar bodies, and increased the amount of ribosomes and mitochondria. Furthermore, the presence of pinocytotic vesicles and the extension of cytoplasmic processes covering the denuded basement membrane strongly suggested a type I epithelium profile. (c) Capillary endothelium showed the first signs of damage on Day 3 and Day 5. (d) Interstitial cells started to proliferate on Days 4 and 5 and invaded empty alveolar spaces. (e) Macrophages were involved from the first day and their phagocytizing activity was maximal on Day 4. The changes observed in mouse lung following BHT are therefore quite similar to other forms of lung injury produced by chemicals. BHT may be a reliable tool to study lung damage and repair.

Stimulation of DNA Synthesis in Mouse Lung Following Intraperitoneal Injection of Butylated Hydroxytoluene

Summary Male Swiss-Webster mice were injected ip with 400 mg/kg of the antioxidant buty-lated hydroxytoluene (BHT). Between 2 and 5 days after BHT, there was a marked increase in the incorporation of thymidine into pulmonary DNA; 7 and 9 days after BHT, incorporation of thymidine fell towards values found in control animals. The increased incorporation of thymidine was accompanied by a net and significant increase in total lung weight and a persistent elevation of total lung DNA. Butylated hydroxytoluene did not stimulate DNA synthesis in liver, kidney, spleen, or gastrointestinal tract. Butylated hydroxytoluene could be used as a tool to study the biochemical events leading to or accompanying stimulated DNA synthesis and cell growth in lung.

Toxicity of butylated hydroxytoluene in mouse following oral administration.

Male Swiss--Webster mice were given 400 mg/kg of butylated hydroxytoluene ([methyl-14C]toluene) by stomach tube. Radioactivity was measured in plasma, lung, liver and kidney from 0.5 h to 10 days later. Radioactivity associated with butylated hydroxytoluene (BHT) or its metabolites was highest in plasma and all tissues examined between 1 and 12 h after administration. After 24 h, less than 1% of the administered dose remained in the lung, kidney or liver. One day after BHT, DNA synthesis in lung increased and, on days 3, 4 and 5, was 6--8 times as high as in controls. DNA content of the lungs almost doubled. Synthesis and net increase of pulmonary DNA were dose-dependent. If BHT was given orally following injection of one single dose of urethane, adenoma formation in lung was enhanced. It is concluded that BHT, given by stomach tube and in doses higher than 100 mg/kg, produces extensive cell proliferation in mouse lung and acts as a promoting agent in adenoma development.

Lung growth in mice after a single dose of butylated hydroxytoluene

Abstract In male Swiss-Webster mice, a single injection of butylated hydroxytoluene (BHT) produced a dose-dependent increase in lung weight. Histopathological changes were well developed 3 days after 500 mg/kg of BHT. After 5 days, there seemed to be a proliferation of many alveolar cells, formation of giant cells, and macrophage proliferation. Lower doses of BHT produced similar, although less extensive changes. The histopathologic alterations were accompanied by biochemical changes: 2 days after BHT, there was a significant increase in lung weight and total amounts of DNA, RNA, and protein. The changes were dose-dependent and the smallest effective dose was 250 mg/kg of BHT. Five days after BHT, the highest doses of BHT (500 and 1000 mg/kg) produced a 1.5- to 2-fold increase in lung weight, total DNA, and protein, and a 3- to 4-fold increase in total pulmonary RNA. The incorporation of thymidine into DNA and of leucine into protein increased from 2 days on after BHT. On the other hand, the incorporation of orotic acid into total pulmonary RNA was lower in the treated animals than in the controls. Administration of a single dose of BHT might offer a convenient tool to study the biochemical changes preceding and/or accompanying stimulated cell growth in lung.

Studies on the pathogenesis of butylated hydroxytoluene-induced lung damage in mice

Experiments were designed to test whether butylated hydroxytoluene (BHT) needs metabolic activation in order to be toxic for mouse lung. Incorporation of thymidine into DNA or activity of pulmonary thymidine kinase was taken to quantitate tissue repair in lung and thus to assess, indirectly, the initial damage. Maximum concentrations of BHT (0.14% of the administered dose) were present in lung between 4 and 8 hr after ip injection of 400 mg/kg. Pretreatment with phenobarbital diminished the toxic effect of BHT, whereas pretreatment with 3-methylcholanthrene or α -naphthylisothiocyanate neither enhanced nor mitigated toxicity. Exposure of animals to 100% oxygen did not alter the effects of BHT upon lung tissue. It is tentatively concluded that the toxic effects of BHT in mouse lung are not due to metabolic activation of the antioxidant but might result from a direct interaction of the BHT with cellular constituents.

Disintegration of lung peroxisomes during differentiation of type II cells to type I cells in butylated hydroxytoluene-administered mice

Ultrastructural and cytochemical changes in peroxisomes of Type II alveolar cells were investigated in butylated hydroxytoluene (BHT)-administered mouse lungs. Male mice were given a single injection of BHT (400 mg/kg, ip) and sacrificed 1 to 7 days later. By means of tracheal infusion, lungs were fixed with a 2% glutaraldehyde or half-strength Karnovsky solution. Type I epithelium was selectively destroyed by BHT and was replaced by cuboidal Type II cells. Type II cells proliferated and some became squamous, extended their cytoplasm, and might differentiate into Type I cells (Hirai, Witschi, and Côté (1977) Exp. Mol. Pathol. 27, 295-308). Peroxisomes, Type II cell constituents, were clustered around and continuous with endoplasmic reticulum. The shape of the peroxisomes became indistinct after Type I cell injury by BHT. Also the density of the matrix was reduced in proportion to the reduction in the peroxidatic activity of catalase. These changes were accompanied by a decrease in the number of peroxisomes. New pinocytotic vesicles, one of the Type I cell characteristics, were generated at the apical and basal cell surfaces. Therefore, these cells had characteristics intermediate between Type I and Type II cells. These findings may indicate further evidence of the origin of Type I cells from Type II cells.

Inhibition of butylated hydroxytoluene-induced mouse lung cell division by oxygen: Time-effect and dose-effect relationships

Mice were injected i.p. with 250 or 400 mg/kg of butylated hydroxytoluene (BHT). In vivo incorporation of thymidine into pulmonary DNA was measured on days 1-7 after BHT. 2, 3 and 4 days after BHT, DNA synthesis was inhibited by a 24-h exposure to 100% oxygen, whereas on days 5, 6 and 7 after BHT, oxygen failed to depress synthesis. A similar pattern was observed when incorporation of leucine into protein was measured: 2 and 4 days after BHT, oxygen decreased leucine incorporation, but had no effect 6 days after BHT or in animals not pretreated with BHT. It is concluded that the cells proliferating early after BHT, the type II alveolar cells, are more susceptible to the cytotoxic effects of oxygen than are interstitial and capillary endothelial cells.

Potentiation of the hepatotoxic responses to chemicals in alloxan-diabetic rats.

Summary Alloxan diabetes enhances the hepatotoxic response of male rats to chloroform and 1, 1, 2-trichloroethane, but not to trichloroethylene nor 1, 1, 1-trichloroethane. Insulin treatment partially protects the animals against the alloxan-induced enhancement of chloroform hepatotoxicity. Alloxan diabetes also enhances the hepatotoxic response to galactosamine but not to beryllium nor alpha-naphthylisothiocyanate.

Enhanced activity of benzpyrene hydroxylase in rat liver and lung after acute Cannabis administration

Abstract Male rats (80–100 g) were given 30–500 mg/kg po of a crude Cannabis resin. Twenty-four hr later, activities of hepatic and pulmonary benzpyrene hydroxylase were enhanced in a dose-dependent manner. When pure Δ 9 -THC (280 and 80 mg/kg) was given, enhanced benzpyrene hydroxylase activity was observed in lung only, and after 280 mg/kg of Δ 8 -THC in liver only.