guanylyl-imidodiphosphate and Hypersensitivity

Basal adenylyl cyclase activity in lung membranes isolated from hypersensitive guinea pigs was increased and more sensitive to stimulation by isoprenaline, GTP and GppNHp when compared to adenylyl cyclase in lung membranes isolated from normal healthy guinea pigs. Maximal forskolin-stimulated adenylyl cyclase activity was unaltered. There was no change in the immunological quantitative amounts of either alpha subunits of the G proteins GiII and Gs (G(o), GiI and GiIII were not present). Maximal pertussis-toxin- and cholera-toxin-catalyzed ADP-ribosylation of Gi alpha and Gs alpha respectively were not significantly altered. The addition of purified protein kinase C to isolated lung membranes resulted in the phosphorylation of the alpha subunit of Gs (stoichiometry was 0.53 mol of 32P incorporated/mol of Gs alpha). Addition of protein kinase C to lung membranes isolated from hypersensitive guinea pigs was equally effective at catalysing the phosphorylation of the alpha subunit of Gs. GppNHp-stimulated and basal adenylyl cyclase activity was also enhanced in isolated tracheal smooth-muscle membranes from hypersensitive guinea pigs. These results suggest that hypersensitive reactions are associated with the improved coupling of the stimulatory G protein (Gs) with adenylyl cyclase.

Topics: Adenylate Cyclase Toxin; Adenylyl Cyclases; Amino Acid Sequence; Animals; Cells, Cultured; Cholera Toxin; Enzyme Activation; GTP-Binding Proteins; Guanine Nucleotides; Guanylyl Imidodiphosphate; Guinea Pigs; Hypersensitivity; Isoproterenol; Lung; Membranes; Molecular Sequence Data; Ovalbumin; Pertussis Toxin; Protein Kinase C; Tetradecanoylphorbol Acetate; Trachea; Virulence Factors, Bordetella

Adenylate cyclase responses to isoproterenol, histamine, 5'-guanylylimidodiphosphate (GppNHp) and NaF were measured in lymphocyte membranes of allergic asthmatic patients and healthy control subjects, just before and 24 h after inhalation challenge with house dust mite allergen or histamine. In the nonacute phase before the challenges, the adenylate cyclase responses in the cell membranes of the patients were not significantly different from those in membranes of the control subjects. House dust mite challenge caused a significant decrease of all adenylate cyclase responses in the cell membranes of the patients by about 40-50%. By contrast, histamine provocation of the patients had no effect on these parameters, nor was there any effect of both challenges on the adenylate cyclase activity of the control membranes. The results indicate that allergen-induced asthmatic reactions may cause nonspecific refractoriness of lymphocyte adenylate cyclase. Since histamine-induced bronchial obstruction had no effect in the patients, it appears that the adenylate cyclase response is specifically modulated by the allergic process.

Topics: Adenylyl Cyclases; Adolescent; Adult; Allergens; Asthma; Bronchial Provocation Tests; Female; Guanylyl Imidodiphosphate; Histamine; Humans; Hypersensitivity; Isoproterenol; Lymphocytes; Male; Receptors, Adrenergic, beta; Sodium Fluoride