Utilization of L-alanine and L-glutamine by lactating mammary gland of the rat. A role for L-alanine as a lipogenic precursor.
1. Lactation is associated with an increase in the arterial blood concentration of L-alanine and L-glutamate, but a decrease in that of L-glutamine compared with the corresponding values for virgin rats. 2. Virgin rats fed a 'cafeteria diet' that induces hyperphagia have increased arterial concentrations of L-alanine, L-glutamate and L-glutamine. During lactation L-alanine and L-glutamate concentrations are even higher. 3. The removal of L-alanine is decreased in hepatocytes from lactating rats fed either a chow or cafeteria diet. 4. Measurements of arteriovenous differences across lactating mammary glands indicate that appreciable amounts of L-glutamine and L-alanine are extracted by the gland. 5. A high proportion of the L-alanine metabolized by isolated acini from fed lactating rats is converted into lipid. 6. Metabolism of L-alanine in acini from starved lactating rats is limited by the activity of pyruvate dehydrogenase. 7. It is concluded that L-alanine and certain other amino acids taken up by the gland in excess of the requirements for protein synthesis can be converted into lipid.
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D005260:Female; D005971:Glutamates / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D066298:In Vitro Techniques; D007774:Lactation; D008055:Lipids / Q000096:biosynthesis; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains
D005971:Glutamates; D008055:Lipids; D005973:Glutamine; D000409:Alanine