XXXX utilization by lactating mammary gland.

@entity1522 @entity1568 @entity1237 @entity535 @entity7222 @entity52283 @entity505 @entity369 @entity11667
@entity1522 utilization comprises two phases, cellular uptake and intracellular metabolism. The paper reviews reports on @entity535 uptake in different species and at different stages of lactation and presents new data on changes at lactogenesis. The relative importance of changes in factors which determine uptake, mammary blood flow, arterial concentration, and mammary extraction, are discussed. In addition to direct incorporation into milk protein, some absorbed @entity1522 are an energy source and @entity505 precursors of other @entity1522 synthesized in mammary cells. Branched-chain @entity1522 and @entity7222 act as @entity1568 precursors in these syntheses. @entity7222 , which is derived partly from absorbed @entity369 , is also a precursor of @entity11667 , a postulated intracellular mediator of hormone action. The question of whether milk protein yield is limited by supply to the mammary gland of certain @entity1522 is discussed. Much evidence indicates the importance of certain essential @entity1522 that are transferred stoichiometrically from blood to milk. Results of experiments involving administration of exogenous @entity52283 to @entity1237 are presented. Increases in milk yield and protein yield are associated with increased rates of mammary blood flow, emphasizing the role of the latter in determining uptake.
