Effect of histamine on cyclic AMP levels in control and antigen-sensitized guinea pig lungs

The effect of histamine on cyclic AMP was investigated in control and antigen-sensitized guinea pig lungs. Although histamine elevated the cyclic AMP levels in a dose-dependent manner in both groups, the response was consistently smaller in the sensitized lungs. In vivo pretreatment of control guinea pigs with histamine decreased the subsequent effect of exogenous histamine on cyclic AMP. Phosphodiesterase activity was not different in the two groups and it was not affected by histamine. These results indicate that the process of antigen sensitization results in an altered cyclic AMP response to histamine.