Effect of sucrose feeding on alpha 1-adrenergic responses in rat liver

A sustained increase in sympathetic nervous system (SNS) activity was induced by substituting a 10% sucrose solution for the drinking water of rats fed laboratory chow ad libitum. The effects of increased SNS activity on alpha 1-adrenergic processes in liver were examined by evaluating three alpha 1-responses, namely, phenylephrine-stimulated ouabain-sensitive 86Rb+ uptake, 45Ca2+ efflux, and glucose release. Sucrose feeding abolished phenylephrine stimulation of ouabain-sensitive 86Rb+ uptake and 45Ca2+ efflux and induced a three- to fourfold reduction in the ability of phenylephrine to stimulate glucose release from liver slices. Pretreatment with 6-hydroxydopamine markedly reduced liver norepinephrine content. When 6-hydroxydopamine was used to prevent the sucrose-induced increase in SNS activity, the changes in 86Rb+ uptake, 45Ca2+ efflux, and glucose release that otherwise followed sucrose feeding were not observed. Sucrose feeding did not alter binding of the alpha 1-antagonist [3H]prazosin to liver cell membrane alpha 1-receptors or displacement of [3H]prazosin by the alpha-agonist epinephrine. These observations suggest that sustained increases in SNS activity may have profound effects on liver alpha 1-adrenergic events that occur subsequent to hormone-receptor interaction.