Baumrucker C R
J Dairy Sci. 1985 Sep;68(9):2436-51. doi: 10.3168/jds.S0022-0302(85)81119-X.
Nutrient provision to the lactating mammary gland involves three factors: blood nutrient concentration, blood flow, and cellular uptake. This paper reviews uptake of amino acids by bovine mammary tissue relative to interorgan blood flows, red blood cell contribution, arteriovenous differences, specific mammary amino acid transport systems, and glutathione and gamma-glutamyl transpeptidase. Recent studies with ruminant amino acid blood fluxes and the role of the red blood cell in providing nitrogenous substrates to tissues have brought to light new considerations of nutrient availability to mammary tissue. Previous studies measured arteriovenous differences to quantitate net amino acid uptake. These studies are considered relative to seven specific and separate amino acid transport systems, some of which have been identified in bovine mammary tissue. Uptake of sulfur amino acids by mammary tissue has been of interest because it appeared that insufficient quantities were provided during lactation. Glutathione, a tripeptide, may be a principle source of cysteine to mammary tissue via mechanisms involving gamma-glutamyl transpeptidase, glutathione, and red blood cells. The paper considers these mechanisms in relationship to amino acid transport systems.
血液营养浓度、血流量和细胞摄取。本文综述了牛乳腺组织对氨基酸的摄取，涉及器官间血流量、红细胞的贡献、动静脉差异、特定的乳腺氨基酸转运系统以及谷胱甘肽和γ-谷氨酰转肽酶。最近关于反刍动物氨基酸血流以及红细胞在为组织提供含氮底物中的作用的研究，揭示了乳腺组织营养可用性的新考虑因素。以往的研究测量动静脉差异以定量氨基酸净摄取量。这些研究是相对于七个特定且独立的氨基酸转运系统进行考量的，其中一些已在牛乳腺组织中得到鉴定。乳腺组织对含硫氨基酸的摄取一直备受关注，因为在泌乳期间提供的量似乎不足。谷胱甘肽是一种三肽，可能通过涉及γ-谷氨酰转肽酶、谷胱甘肽和红细胞的机制，成为乳腺组织半胱氨酸的主要来源。本文探讨了这些机制与氨基酸转运系统的关系。
