Food restriction modulates beta-adrenergic-sensitive adenylate cyclase in rat liver during aging.
Adenylate cyclase activities were studied in rat liver during post-maturational aging of male Fischer 344 rats fed ad libitum or restricted to 60% of the ad libitum intake. Catecholamine (10(-5) M epinephrine, isoproterenol, or norepinephrine)-stimulated adenylate cyclase activity increased by 200-300% between 6 and 24-27 mo of age in ad libitum-fed rats, whereas in food-restricted rats catecholamine response increased by only 58-84% between 6 and 30 mo. In ad libitum-fed rats, glucagon (10(-5) M)-stimulated enzyme activity also increased by 40% between 6 and 12 mo and in restricted rats a similar age-related increase was delayed until 18 mo. beta-Adrenergic receptor density (Bmax, determined from saturation binding of the beta-adrenergic antagonist l-[125I]iodopindolol) increased by 50% between 6 and 24 mo in livers from ad libitum-fed but not food-restricted rats and showed a highly significant correlation with maximal isoproterenol-stimulated adenylate cyclase activity over the post-maturational life span. Age-related increases in unstimulated (basal) adenylate cyclase activity and nonreceptor-mediated enzyme activation (by guanine nucleotides, fluoride, and to a lesser extent forskolin) were retarded by food restriction. The results demonstrate that food restriction diminishes a marked age-related increase in beta-adrenergic-sensitive adenylate cyclase activity of rat liver. Alterations of adrenergic-responsive adenylate cyclase with age and the modulatory effects of food restriction appear to be mediated by changes in both receptor and nonreceptor components of adenylate cyclase.
Katz
M S
MS
Department of Medicine, University of Texas Health Science Center, San Antonio.
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000375:Aging / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D004789:Enzyme Activation; D005508:Food Deprivation / Q000502:physiology*; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D011943:Receptors, Adrenergic, beta / Q000378:metabolism / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D000262:Adenylyl Cyclases