[Glucagon receptor binding and its effect on the cAMP level in isolated rat and chicken hepatocytes].

The binding sites to glucagon with KD 10(-9) M in rat and chicken isolated hepatocytes and with KD 10(-7) M in chicken hepatocytes only where revealed. The first, but not the second binding sites where decreased in their affinity by the adding of GTP nonhydrolyzing analogue Gpp(NH). Glucagon activated the cAMP accumulation in rat and chicken hepatocytes in dose-depended manner. The dose-response curve being plateau after maximum in rats and decreased in chicken. Glucagon inserted an inhibiting effect when occupying chicken-specific sites of binding with KD 10(-7) M. The nature of these binding sites and mechanism of glucagon inhibiting effect on the cAMP accumulation are discussed.