Effect of Protein Intake on Amino Acid Transport and Adenosine 3′,5′-Monophosphate Content in Rat Liver

Abstract

The effects of protein intake on hepatic amino acid transport and cyclic AMP content have been determined in the rat. Within 1 day after feeding an 80% casein diet ad libitum, net transport of α-aminoisobutyric acid in liver slice preparations was doubled; the response decreased thereafter. Feeding one high protein meal to rats trained to eat a normal diet for 3 hours daily doubled and tripled hepatic AIB uptake at 0.5 and 1 hour, respectively; thereafter uptake decreased with time but at 24 hours was still slightly above that in control slices. Cycloleucine transport also increased rapidly and then declined with time in slices from trained rats fed one high protein meal. Adrenalectomized rats fed a high protein diet ad libitum for 1 to 5 days responded as did intact rats. Hepatic adenosine 3′,5′-monophosphate concentration increased by factors of 2 and 2.5 within 15 and 30 minutes, respectively, after feeding one high protein meal to rats trained to eat once a day. This increase was maintained for several hours after feeding began but declined therafter. Stimulation of amino acid transport by feeding a high protein meal may be the result of a small, but rapid, increase in hepatic adenosine 3′,5′-monophosphate content.