Modulation of guinea-pig lung adenylate cyclase by ovalbumin sensitization

1. The regulation of lung adenylate cyclase was investigated in guinea pigs sensitized with high dose (300-500 micrograms kg-1) ovalbumin to raise IgG(I) and low dose (2.8-4.0 micrograms kg-1) to raise to IgG/IgE (II) antibodies. 2. Basal activity of sensitized II (IgG/IgE antibodies) lung adenylate cyclase was approximately double that of the control values. 3. Guanosine 5'-triphosphate (GTP) was a potent activator of adenylate cyclase from the sensitized II (IgG/IgE) lung membranes. 4. The sensitivity of lung membrane adenylate cyclase to stimulation by beta-adrenoceptor agonists or VIP was reduced whereas no significant difference was observed with histamine or bradykinin on the sensitized II membranes. 5. Possible mechanisms involved in the increase in basal activity and in the decreased sensitivity to beta-adrenoceptor- and VIP-mediated stimulation of adenylate cyclase by ovalbumin sensitization of guinea-pig lung membranes are discussed.