K Woie, E Westerberg and RK Reed
Department of Physiology, University of Bergen, Norway.

Interstitial fluid pressure (Pif) has recently been found to play an important role in edema formation in acute airway inflammation. Because airway inflammation is important in the pathogenesis of asthma, Pif was measured in rat trachea after albumin challenge to rats previously sensitized to chicken egg albumin. In pentobarbital anesthesia (50 mg/kg intraperitoneally) sensitized rats received an intravenous infusion of either saline or albumin, which circulated for 4 min. Circulatory arrest was then induced with saturated KCl intravenously to prevent further edema formation, which will increase Pif and thereby possibly cause an underestimation of an increased negativity of Pif. Pif was measured with sharpened glass capillaries (diameter 3-6 micrometer) connected to a servo-controlled counter pressure system. Pif was -1.3 +/- 0.4 mm Hg in controls and -5.8 +/- 0.5 mm Hg in sensitized rats (p < 0.01) after allergen challenge. Airway resistance was measured to verify the occurrence of airway narrowing and increased significantly in sensitized rats after allergen challenge but did not change in controls. The experimental anti-inflammatory drug, alpha- trinositol (D-myo-inositol-1,2,6-trisphosphate, 10 mg), given before or after allergen challenge abolished the increased negativity of Pif (p < 0.05), while hydrocortisone (6.25 mg) had no effect. Thus, allergen challenge is associated with a lowering of Pif, which was abolished by alpha-trinositol.