Uterine beta-adrenergic receptors in allogeneic and syngeneic pregnancy.

Two different mechanisms of regulation in uterine beta-adrenergic receptors in allogeneic pregnancy (AP) and syngeneic pregnancy (SP) are described in this work. Firstly we noted changes in beta-adrenergic sensitivity to isoproterenol in AP, while in SP differences in uterine reactivity to isoproterenol were found. In binding assays with the beta-antagonist [3H]dihydroalprenolol, changes in beta-receptor affinity were seen in AP, while in SP the maximal number of binding sites is altered. In addition, there are differences in uterine concentrations of cyclic AMP in both types of pregnancies as well as in the nucleotide response to isoproterenol. The differences in the reactivity and expression of uterine beta-adrenoceptors in both types of pregnancies may be due to a distinctive immunological role of the semiallogeneic fetus in AP.