Effects of amphetamine on immune-mediated lung inflammatory response in rats.

OBJECTIVE: The present study analyzed the effects of acute amphetamine (AMPH) treatment on immune-mediated lung inflammatory response in rats. METHODS: There were four experiments. In the first and second experiments, rats were treated with AMPH (1 mg/kg) or 0.9% NaCl, and locomotor activity (experiment 1) and serum AMPH concentrations (experiment 2) were measured 1 or 12 h after treatment. In the third experiment, rats which were immunized with ovalbumin (OVA) were treated 14 days later with 0.9% NaCl or AMPH (1 mg/kg). Twelve hours after these treatments, all animals were submitted to challenge by 1% OVA inhalation being analyzed afterwards for bronchoalveolar lavage fluid (BAL), peripheral blood and bone marrow cellularity. In the fourth and final experiment, rats were treated and studied as for experiment 3, except that half of the animals within each group were previously treated with metyrapone prior to the OVA challenge. RESULTS: In the non-immunized rats, AMPH treatment induced an increase in locomotor activity synchronized to high serum AMPH concentrations 1 h after, but not 12 h after treatment. In OVA-challenged rats, AMPH treatment decreased the total number of inflammatory cells, recovered in both BAL and peripheral blood and increased the total number of bone marrow cells. These effects, observed 1 day after OVA challenge, were abrogated by previous metyrapone treatment. CONCLUSION: AMPH treatment changed HPA-axis responsiveness to the stress condition imposed by the OVA challenge decreasing lung and blood leukocytes cellularity most probably via corticosterone actions on bone marrow activity.

Yangambin, a lignan obtained from Ocotea duckei, differentiates putative PAF receptor subtypes in the gastrointestinal tract of rats.

We investigated the presence of PAF receptor subtypes in the tissues of the gastrointestinal tract, airways, blood vessels and in murine macrophages. For this purpose we have used a competitive PAF receptor antagonist, yangambin (YAN), extracted from the Brazilian plant "louro de cheiro" (Ocotea duckei Vattimo). Rat duodenum, jejunum, ileum, colon, stomach fundus, trachea and bronchia were removed and 1.5-2 cm muscle segments from those regions were mounted in a 10 ml organ bath with aerated physiological solution at 37 degrees C. PAF evoked a contraction of the rat jejunum, ileum, colon and stomach fundus. The contraction was slow and resistant to wash and was followed by desensitization to further doses of PAF. Contractions induced by PAF (10(-6) M) were inhibited by YAN (10(-7) to M-2 x 10(-5) M) and WEB 2086 (10(-6) m to M-5 M) in rat jejunum, ileum and colon but not in the stomach fundus. In the rat stomach fundus only WEB 2086 (5 x 10(-6) M) was able to block PAF-induced contraction. The contractions induced by acetylcholine, histamine, 5-hydroxytryptamine and vasopressin were not inhibited by prior administration of YAN. Yangambin also significantly inhibited PAF-induced vascular permeability in rat duodenum, jejunum, ileum, colon, and mesentery. Yangambin significantly inhibited PAF-induced lipid body formation in mice peritoneal macrophages. We suggest that YAN is a selective PAF antagonist which is able to discriminate putative PAF receptors subtypes present in the stomach fundus.

Modulation of hypersensitivity reaction by lipids given orally.

The effect of lipids administration by gavage (0.4% body weight) given daily during four weeks on the hypersensitivity reaction in trachea, upper and lower bronchi, liver, kidney, mesentery, and pancreas was investigated in male rats. The plasma exudation was assessed by using Evans blue (EB) dye extravasation method. There was a significant difference in the permeability of the organs in nonimmunized rats. The immunization increased the vascular permeability and the response with the organs varied greatly. The effect of lipids on anaphylactic reaction was compared to those of untreated rats (control group). The EB extravasation was significantly increased in the trachea obtained from rats treated with cocoa butter and soybean oil. In the upper bronchi of rats treated with soybean oil, the EB extravasation was increased. However, in the lower bronchi, none of the treatments with lipids changed the extravasation of EB. The same was observed in the liver and kidney. The animals treated with lipids by gavage did not present differences in EB extravasation in the mesentery. However, in the pancreas and duodenum, the treatment with fish and soybean oils and cocoa butter markedly lowered EB extravasation.

Nitric oxide modulates Na+, K+-ATPase activity through cyclic GMP pathway in proximal rat trachea.

The present work demonstrated that nitric oxide (NO) modulates Na+, K+-ATPase activity in the proximal rat trachea. Sodium nitroprusside induced concentration-dependent (10-100 microM) stimulation in proximal trachea Na+, K+-ATPase activity. The effect was specific for Na+, K+-ATPase since Mg-ATPase activity was unaffected. This NO-donor changed neither Na+, K+-ATPase nor Mg-ATPase activity in the distal segment. The modulatory action on Na+, K+-ATPase induced by sodium nitroprusside was linked to an increase in nitrates/nitrites and cyclic GMP levels in proximal segments. Modulation of proximal Na+, K+-ATPase activity by sodium nitroprusside was mimicked by S-nitroso-N-acetylpenicillamine (100 microM) and 8-bromo-cyclic GMP (100 microM). Both sodium nitroprusside and 8-bromo-cyclic GMP effects on Na+, K+-ATPase activity of proximal segments of trachea were blocked by 2 microM of KT 5823 (a cyclic GMP-dependent protein kinase inhibitor), but not by 0.5 microM of KT 5720 (a cyclic AMP-dependent protein kinase inhibitor). Both kinase inhibitors decreased proximal Na+, K+-ATPase activity, but did not change Mg-ATPase activity. Okadaic acid (1 microM), a phosphatase-1 inhibitor, increased proximal Na+, K+-ATPase but not Mg-ATPase activity. The effect of okadaic acid was non-additive with that of 8-bromo-cGMP on Na+, K+-ATPase activity. Our results suggest that NO modulates proximal rat trachea Na+, K+-ATPase activity through cyclic GMP and cyclic GMP-dependent protein kinase.

Contractile responses of proximal and distal trachea segments isolated from rats subjected to immunological stimulation: role of connective tissue mast cells.

1. Anaphylaxis-induced contractions of proximal and distal tracheal segments isolated from 14-day ovalbumin (OA)-sensitized rats were studied. 2. OA-induced contractions in distal segments were significantly greater than those observed in proximal segments. 3. Pretreatment of the rats with compound 48/80 or with sodium cromoglycate (SCG) aerosolization significantly reduced OA-induced contractions of trachea distal segments, whereas the contractions of proximal segments were reduced only by compound 48/80. 4. Mepacrine reduced and indomethacin increased the OA-induced contractions in all tracheal segments. Nor-dihydroguaiaretic acid increased the OA-induced contractions in distal tracheal segments, whereas dazoxiben inhibited the contractions in these same segments; neither of these drugs had any effect on the contractions in proximal tracheal segments. 5. The depletion of connective tissue mast cells and subsequent in vitro treatment with indomethacin increased the OA-induced contractions in both segments. 6. We conclude that the contractions of tracheal muscle from OA-sensitized rats depends on the topographic and anatomical origin of the airway tissue. 7. Mediators released by connective tissue mast cells in proximal and distal segments play a pivotal role in this response and may account for variations in the intensity of contraction seen after the addition of OA.

Estudo comparativo de métodos analíticos para dosagem de metemoglobina no sangue / Comparative study among analitycal methods to blood methemoglobin determination

A exposição ocupacional aos solventes anilina e nitrobenzeno é monitorizada biologicamente através da determinação dos níveis de metemoglobina sanguínea. O máximo teor de metemoglobina permitido nas amostras de sangue dos indivíduos expostos é 5% da hemoglobina total, obrigando a utilização de métodos analítico-sensíveis e precisos. Dois métodos analíticos utilizados na determinação de metemoglobinemia (Hegesh et all. e Evely & Malloy. Mod. Beutler), rotineiramente utilizados nos laboratórios de hematologia e Toxicologia da Faculdade de Farmácia da UFMG, foram estudados objetivando estabelecer o mais adequado para ser utilizado na monotirazação biológica de indivíduos expostos ocupacionalmente à anilina ou nitrobenzeno. Apenas o método de Hegesh et all. mostrou-se adequado para os objetivos propostos. Foram detectados valores tão baixos quanto 0,9% de metemoglobina e os coeficientes de variação intra e interensaio foram, respectivamente, 3,87% e 3,25%.