ovalbumin and Spasm

1. In order to examine whether K+ channels play a role in antigen-induced airway responses, the effect of K+ channel blockers on antigen-induced airway smooth muscle contraction and mediator release was examined in vitro in guinea-pigs actively sensitized with ovalbumin (OA). 2. Tracheal strips from sensitized animals were suspended in organ baths under a resting tension of 1 g and isometric tension was continuously measured. Cumulative concentration-response curves to OA (0.1-1000 ng ml-1) or histamine (10 nM-1 mM) were obtained in the presence and absence of K+ channel blockers. 3. OA (10, 100 or 1000 ng ml-1) was incubated with minced lung tissues from the same animals for 15 min in the presence and absence of K+ channel blockers, and released histamine and leukotriene C4 (LTC4) in the incubating medium were measured. 4. Apamin, a small conductance Ca(2+)-activated K+ channel (PK,Ca) blocker, (0.1, 0.3 and 1 microM) significantly inhibited OA-induced smooth muscle contraction, while charybdotoxin (ChTX, 10 nM), an intermediate and large conductance PK,Ca blocker, and iberiotoxin (IbTX, 3 nM), a large conductance PK,Ca blocker, were without effect. Apamin (0.3 microM) had no effect on exogenously administered histamine-induced airway smooth muscle contraction, suggesting that the inhibition of OA-induced contraction by apamin did not occur at the smooth muscle level. 5. The inhibition of OA-induced contraction by apamin (0.3 microM) was not significantly affected by pretreatment with a leukotriene antagonist, ONO-1078 (10 microM), but was abolished by pretreatment with a histamine H1-receptor blocker, pyrilamine (1 microM). 6. Apamin by itself (up to 0.1 MicroM) had no effect on spontaneous histamine release from minced lung tissues. Histamine release induced by low and intermediate concentrations of OA (10 and 100 ng ml-1)was significantly suppressed by apamin pretreatment (P<0.05 and P<0.001), whereas LTC4 release was not affected. ChTX (0.1 MicroM) and IbTX (10 nM) had no significant effect on either spontaneous or OA (100 ng ml-1)-induced histamine release.7. These results suggest that apamin partially but substantially inhibits antigen-induced smooth muscle contraction, presumably by inhibiting antigen-induced histamine release from airway mast cells through small conductance PKca closure.

Topics: Animals; Antigens; Apamin; Charybdotoxin; Guinea Pigs; Histamine; Histamine H1 Antagonists; In Vitro Techniques; Indomethacin; Inflammation Mediators; Isometric Contraction; Leukotriene Antagonists; Male; Mast Cells; Muscle Contraction; Muscle, Smooth; Ovalbumin; Potassium Channels; Scorpion Venoms; Spasm; Trachea

The effect of antigen (ovalbumin) challenge on pulmonary hemodynamics, bronchoconstriction, and fluid filtration was investigated in Ringer's-perfused (non-recirculating) lungs that had been passively sensitized in vitro. Bolus ovalbumin injection (30 micrograms) produced immediate increases in pulmonary arterial pressure, peak intratracheal pressure, and lung weight within 1 min and secondary marked increases in intratracheal pressure and lung weight from 120 to 200 min. Electron microscopy of antigen-challenged isolated lungs showed evidence of both septal and intraalveolar edema. Ionophore A23187 (100 micrograms) challenge of nonsensitized lungs produced immediate pulmonary responses similar to antigen, whereas secondary increases in lung weight were smaller. Arachidonic acid pretreatment (1 microM) potentiated immediate antigen-induced increases in intratracheal pressure but did not affect pulmonary responses to ionophore challenge. Putative mediators of anaphylaxis including histamine, leukotrienes B4, C4, D4, and E4, platelet-activating factor, and substance P produced immediate changes in pulmonary arterial and/or intratracheal pressure similar to antigen challenge. Only platelet-activating factor and substance P partially mimicked the secondary edema formation noted following antigen challenge. Thus, antigen challenge in in vitro sensitized guinea pig lungs produced both immediate and secondary responses characterized by increases in vascular pressure, airway pressure, and edema formation. This occurred in the absence of circulating blood-formed elements and without a massive influx of cells. Synergism between mediators such as histamine, the leukotrienes, platelet-activating factor, and substance P released following antigen challenge may be necessary to produce the complete pathophysiological sequelae associated with antigen challenge in the perfused guinea pig lung.

Topics: Anaphylaxis; Animals; Antigens; Bronchi; Calcimycin; Constriction, Pathologic; Guinea Pigs; Hemodynamics; Immunization; In Vitro Techniques; Lung; Microscopy, Electron; Ovalbumin; Pulmonary Artery; Pulmonary Edema; Spasm

1. Human lung tissue, passively sensitized with reaginic antibodies, released prostaglandins E(1), E(2) and F(2alpha) in addition to histamine and slow reacting substance (SRS-A), when exposed to the appropriate antigen. No rabbit aorta contracting substance (RCS) was detected.2. Experiments with rats and guinea-pigs showed that the release of RCS is not confined to anaphylactic reactions mediated by non-reaginic antibodies but may be a feature of anaphylaxis in guinea-pigs alone.3. Human lung tissue gently agitated with a blunt nylon rod liberated an E-type prostaglandin and RCS in addition to histamine and SRS-A.4. Human isolated bronchial muscle was contracted by RCS.5. Disodium cromoglycate antagonized the release of prostaglandins during anaphylaxis but not during agitation of human lung tissue, whereas indomethacin blocked the release of prostaglandins during agitation and anaphylaxis.6. The release of an E-type prostaglandin during anaphylaxis in human lung tissue, which inhibits the further release of histamine could be another example of the regulatory role of prostaglandins in body functions.

Topics: Anaphylaxis; Animals; Aorta; Bordetella pertussis; Bronchi; Cromolyn Sodium; Histamine; Humans; Immunoglobulin E; In Vitro Techniques; Indomethacin; Lung; Muscle Contraction; Muscle, Smooth; Ovalbumin; Prostaglandins; Rabbits; Rats; Spasm; SRS-A; Tissue Extracts