title: Age-related change in adrenergic regulation of glycogen phosphorylase in rat hepatocytes.
abstract: The effects of development on adrenergic regulation of glycogenolysis were studied in rat liver. In isolated hepatocytes, the activation of glycogen phosphorylase by alpha-adrenergic stimulation decreased moderately with advancing age. However, activation by beta-adrenergic receptors more markedly declined and almost disappeared in isolated hepatocytes from 6-month-old rats. Furthermore, the ability to glucagon to stimulate phosphorylase activity and cAMP generation was found to decrease with increasing age. The age-related changes in the pattern of stimulation of glycogen phosphorylase by catecholamines in isolated hepatocytes were accompanied by parallels changes in the numbers of alpha 1- and beta-adrenoceptors in membranes prepared from the isolated hepatocytes. A progressive decrease in the total number of alpha 1-receptors measured with [3H]-prazosin and beta-receptors measured with [125I]cyanopindolol (CYP) was found with increasing age. The loss of beta-adrenergic receptors was much more dramatic. Our results suggest that age-related alterations of hepatic glycogen phosphorylase activation by catecholamines may in part be explained by the changes in the expression adrenergic receptors.
mesh_terms: D000375:Aging; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D008297:Male; D006005:Phosphorylases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism
chemical_list: D002395:Catecholamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D005934:Glucagon; D006005:Phosphorylases