Involvement Of Lipoxygenase Research Articles

Indomethacin enhances the effect of histamine on airways resistance in the anaesthetized guinea-pig.

In anaesthetized guinea-pigs intravenous histamine caused an increase in airways resistance (RA) and a fall in dynamic compliance (CDyn). Indomethacin (1 mg kg-1, i.v.) significantly enhanced the effect of histamine on RA. Indomethacin also increased the basal RA and the RA response to a histamine infusion. The effect of indomethacin on CDyn was less consistent but here also there was a trend for an increased response to histamine. Sodium carbonate (the vehicle for indomethacin, 0.05 ml 100 mM solution) had no effect on RA or CDyn in control experiments. Propranolol (0.1 mg kg-1, i.v.) enhanced the effect of histamine on RA in animals pretreated with either indomethacin or Na2CO3 vehicle, but the effect was more consistent in indomethacin pretreated animals. Indomethacin also tended to enhance the effect of histamine on RA in animals pretreated with reserpine or BW755c but it had little effect on the CDyn response to histamine. The results show that indomethacin augments the responsiveness of the airways to histamine in the anaesthetized guinea-pig. The results with propranolol and reserpine suggest that an operational beta-adrenergic system is not required for the effect of indomethacin on RA. No confirmation for lipoxygenase involvement was obtained with the lipoxygenase inhibitor, BW755.

The involvement of lipoxygenase and antioxidants in pathogenesis of powdery mildew on tobacco plants

Tobacco plants (cv. Michal) exhibited between a four- to seven-fold increase in lipoxygenase activity as a result of infection with the powdery mildew fungal pathogen, Erysiphe cichoracearum. Isolated hyphae and conidia of the pathogen had a very low activity of the enzyme. Increased enzyme activity was detectable at 2 to 3 days after inoculation, reached a maximal level at 11 days after inoculation, and gradually declined thereafter. Elevated lipoxygenase activity in homogenates of affected leaves was associated with corresponding increments in peroxides, endogenic antioxidant substances and carotene-bleaching activity. Young mildewed leaves also exhibited a × 4·5, × 2·5 and × 2 increase in leakage of electrolytes, sugars and proteins, respectively, as against non-infected tissue. Exogenous application of the antioxidant α-tocopherol (Vitamin E) to leaves of normal tobacco plants reduced both lipoxygenase activity and mildew development. Tocopherol had no adverse effect on conidial germination in vitro. It is suggested that the marked increase in lipoxygenase activity induced in tobacco by Erysiphe cichoracearum might cause a distortion of host membranous structures which, in turn, would bring about two major physiological consequences: (a) transfer of solutes from mesophyll host cells into fungal haustoria in epidermal cells, and (b) enhanced senescence and necrotization of the invaded host tissue.

Selective release of histamine from rat mast cells by compound 48-80 and anitgen.

Selective release of histamine from rat mast cells by compound 48-80 and anitgen.