Beta-adrenoceptor changes in submandibular glands of old mice.

The hypothesis that modifications in beta-adrenergic receptors may be responsible for age-dependent change previously observed in vivo, has been investigated. Beta-adrenoceptor characteristics of submandibular glands of mice were studied by using the beta-adrenergic antagonist (-)-[3H]dihydroalprenolol. Data from such studies indicated the presence of two functional populations of binding sites in membrane preparations from young animals, displaying high and low affinity, respectively. Experiments performed on old mice membrane preparations revealed a 50% decrease in the high-affinity population receptor number when compared to the preparations from young animals. However, the affinity did not change significantly with advancing age. With regard to the low-affinity population, no statistically significant changes were observed. From these data it can be reasonably assumed that beta-adrenoceptor alteration during ageing may play a major role in the age-dependent impairment of beta-adrenergic responses in vivo.