Influence of age on the beta 1- and beta 2-adrenergic receptors in rat liver.
The influence of maturation and aging on beta receptors in rat liver was studied. Competition binding experiments with the nonselective beta-antagonist propranolol and the subtype selective antagonists ICI 118,551 (beta 2) ICI 89,406 (beta 1), and CGP 20,712A (beta 1) revealed the presence of a mixed beta 1 and beta 2 receptor population in crude plasma membrane preparations from livers of newborn, mature, and senescent rats. The percentage of beta 1 receptors was lowest in livers from newborn rats and was increased in livers from mature and senescent rats. This increase is caused by a decrease in beta 2 receptor density on maturation, although the beta 1 receptor density is nearly constant throughout the life span of the rat. Isoproterenol-stimulated adenylate cyclase activity was inhibited in livers from senescent rats by propranolol and ICI 118,551 and to a lesser extent by ICI 89,406 and CGP 20,712A. The isoproterenol-stimulated glucose output in hepatocytes from senescent rats was inhibited concentration dependently by propranolol, ICI 118,551, ICi 89,406, and CGP 20,712A. From these results we conclude that beta 1 and beta 2 receptors are present in livers from rats of the three age groups and that the beta 1 to beta 2 receptor ratio is increased in livers from mature and senescent rats compared with newborn rats. Both beta receptor subtypes are linked to the cAMP second messenger system in newborn and senescent rats; beta 1 and beta 2 receptors are equally involved in the regulation of glycogenolysis in hepatocytes from senescent rats.
Van Ermen
A
A
Heymans Institute of Pharmacology, Gent, Belgium.
Van de Velde
E
E
Vanscheeuwijck
P
P
Fraeyman
N
N
D000262:Adenylyl Cyclases / Q000378:metabolism; D000375:Aging; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000201:enzymology; D007093:Imidazoles / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008112:Liver Glycogen / Q000378:metabolism; D008297:Male; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011412:Propanolamines / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000378:metabolism*
D007093:Imidazoles; D008112:Liver Glycogen; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; C047975:cyanopindolol; D011433:Propranolol; D010869:Pindolol; C025716:ICI 89406; C049763:CGP 20712A; D000262:Adenylyl Cyclases