Extracellular amino acid effects on milk protein synthesis and intracellular amino acid pools with bovine mammary cells in culture.
Increases in free intracellular amino acids are associated with increased protein synthesis. Responses in synthesis of beta-casein and beta-lactoglobulin and of intracellular amino acid pools to graded concentrations of amino acids in the medium were observed. Mammary tissue from two Holstein cows was dispersed and cultured for 18 h with Eagle's minimal essential medium containing 1, 3, 5, or 7 times the basic concentration of amino acids. Synthesis of beta-casein and beta-lactoglobulin increased with concentration of amino acids in the medium. Intracellular pools of amino acids not provided by the medium (serine, proline, alanine, glycine, glutamic acid, ornithine) generally decreased with increased concentrations of amino acids in the medium, the exception being ornithine which increased with extracellular amino acids. Lysine, histidine, tyrosine, leucine, valine, phenylalanine, isoleucine, arginine, and threonine intracellular pools increased with increased amino acids in medium. Intracellular cystine responded with a small linear increase to increased amino acids in the medium, while intracellular tryptophan and methionine did not respond, indicating potential limitations from these amino acids.
D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002364:Caseins / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D005260:Female; D007782:Lactoglobulins / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism; D008894:Milk Proteins / Q000096:biosynthesis*
D000596:Amino Acids; D002364:Caseins; D007782:Lactoglobulins; D008894:Milk Proteins