Desensitization of canine histamine H2 receptor expressed in Chinese hamster ovary cells

Canine histamine H2 receptor DNA was transfected into Chinese hamster ovary cells using an expression vector. Expression of H2 receptors was demonstrated by immunoblotting with specific antibodies and the binding of tiotidine, an H2 receptor antagonist. H2 receptor-specific cAMP production was observed only in the cells expressing canine H2 receptor with 10(-9)-10(-4) M histamine in a dose-dependent manner. Preincubation of transfected cells with 10 microM histamine for 10 min or 60 min at 37 degrees C decreased both the maximal response and the sensitivity of the subsequent histamine-stimulated cAMP production, showing desensitization. Under these circumstances, tiotidine binding was decreased by 25% in intact cells. A similar decrease in the tiotidine binding was observed also in the membrane without changes in the affinity, whereas no decrease in total H2 receptor number was observed. Thus, desensitization of histamine H2 receptor was associated with the sequestration of receptors.