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Evidence for a decrease in the efficiency of beta-receptor coupling to adenylate cyclase in liver membranes from sucrose-fed rats.

C J Lynch·M L Steer·M R Connors·R A Schatz·R C Deth
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Abstract

Sucrose feeding has been shown previously to alter the plasma concentration of several factors which may regulate beta-adrenergic receptors, including corticosteroids and insulin as well as altered sympathetic nervous system (SNS) tone. For this reason we initiated a study of the effects of sucrose feeding on the beta-adrenergic receptor-adenylate cyclase system in rat liver plasma membranes. Beta-Adrenergic responsiveness was monitored by measuring isoproterenol stimulation of adenylate cyclase activity, while beta-adrenergic receptor characteristics were evaluated by analyzing [125I]iodocyanopindolol [( 125I]CYP) binding. Rats fed rat chow ad lib. supplemented by drinking water containing 10% sucrose solution exhibited a 50-75% reduction in hepatic isoproterenol-sensitive adenylate cyclase activity. This effect of sucrose was also observed in adrenalectomized (ADX) and 6-hydroxydopamine-pretreated animals, ruling out a causal role for corticosteroids or the sympathetic nervous system respectively. No effect was observed on basal, glucagon-, fluoride- or GTP-stimulated adenylate cyclase. A small but significant decrease in [125I]CYP specific binding capacity was observed in liver membranes prepared from sucrose-fed ADX rats, whereas no change in [125I]CYP binding capacity was observed in in sucrose-fed normal rats. These observations suggest that beta-receptor to adenylate cyclase coupling efficiency is decreased by the sucrose diet. The activities of two membrane-associated phospholipid methyltransferases and the content of endogenous S-adenosylmethionine in liver were reduced by sucrose feeding, implying a defect in the methylation pathway for phosphatidylcholine synthesis. The possible relationship between this latter finding and the observed decrease in beta-adrenergic receptor to adenylate cyclase coupling efficiency is discussed.

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Adenylyl CyclasesAnimalsCell MembraneFemaleIn Vitro TechniquesIodocyanopindololIsoproterenolLiverMembrane FluidityMethylationPhospholipidsPindololRatsRats, Inbred StrainsReceptors, Adrenergic, betaSucroseJournal ArticleResearch Support, Non-U.S. Gov't

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C J Lynch, M L Steer, M R Connors, R A Schatz, R C Deth. 1985-03-01. Evidence for a decrease in the efficiency of beta-receptor coupling to adenylate cyclase in liver membranes from sucrose-fed rats.. https://doi.org/10.1016/0006-2952(85)90255-2

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