INCREASE IN VASCULAR-PERMEABILITY PRODUCED IN RAT AIRWAYS BY PAF - POTENTIATION BY ADRENALECTOMY

1 The effect of bilateral adrenalectomy on the sensitivity of blood vessels in rat airways to mediators that increase vascular permeability was examined. 2 An increase in vascular permeability was induced by intravenous platelet activating factor (PAF, 50, 100, 500, 1000mg kg-1) and measured by quantifying the extravasation of Evans blue dye. 3 PAF consistently increased the amount of Evans blue extravasation in the larynx, trachea, main bronchi and intrapulmonary airways in sham-operated rats. 4 The magnitude of this extravasation was significantly greater in the larynx (P < 0.05), trachea (P < 0.05) and main bronchi (P < 0.05) of the adrenalectomized rats than it was in these tissues of the sham-operated rats. 5 When adrenalectomized rats were given subcutaneous dexamethasone (0.2 mg kg-1 4h before PAF) the amount of plasma extravasation produced by PAF was decreased to the level of the sham-operated rats. 6 We conclude that adrenalectomy potentiates the increase in airway vascular permeability induced by PAF in rats and that this effect may be due to the depletion of endogenous corticosteroids.