Gibson J B, Berry G T, Mazur A T, Palmieri M J, Reynolds R A, Segal S
Division of Biochemical Development and Molecular Diseases, Children's Hospital of Philadelphia, Pennsylvania, USA.
Biochem Mol Med. 1995 Jun;55(1):8-14. doi: 10.1006/bmme.1995.1025.
In order to test the assumption that red blood cell (RBC) uridine diphosphate galactose content is regulated in part by dietary galactose and to help comprehend factors influencing RBC and white blood cell (WBC) uridine diphosphate hexose concentrations in vivo, oral loading studies were performed with 50 g of galactose or 75 g of glucose in normal adults. While elevations of blood glucose did not influence RBC or WBC UDPhexose levels, increased blood galactose concentrations caused transient increases in both RBC and WBC UDPgalactose. In both RBC and WBC, the UDPgalactose-4-epimerase was rate limiting. In comparison to RBC, WBC had larger changes in UDPgalactose levels, synthesized additional UDPglucose through the action of UDPglucose pyrophosphorylase and began to restore the equilibrium ratio between UDPglucose and UDPgalactose concentrations while the plasma galactose level was still increasing. Thus, galactose ingestion alters the steady-state levels of UDPhexoses in circulating cells. The modulation of UDPglucose and UDPgalactose concentrations, occurring after the presentation of galactose to cells, as a result of the combined actions of GALT and UDPgalactose-4-epimerase, may be important in determining rates of synthesis of complex glycoconjugates.
为了验证红细胞（RBC）尿苷二磷酸半乳糖含量部分受膳食半乳糖调节这一假设，并帮助理解体内影响红细胞和白细胞（WBC）尿苷二磷酸己糖浓度的因素，对正常成年人进行了口服50 g半乳糖或75 g葡萄糖的负荷试验。虽然血糖升高并未影响红细胞或白细胞的尿苷二磷酸己糖水平，但血半乳糖浓度升高导致红细胞和白细胞的尿苷二磷酸半乳糖均出现短暂升高。在红细胞和白细胞中，尿苷二磷酸半乳糖-4-表异构酶均为限速酶。与红细胞相比，白细胞的尿苷二磷酸半乳糖水平变化更大，通过尿苷二磷酸葡萄糖焦磷酸化酶的作用合成了额外的尿苷二磷酸葡萄糖，并在血浆半乳糖水平仍在升高时开始恢复尿苷二磷酸葡萄糖和尿苷二磷酸半乳糖浓度之间的平衡比例。因此，摄入半乳糖会改变循环细胞中尿苷二磷酸己糖的稳态水平。在半乳糖进入细胞后，由于半乳糖-1-磷酸尿苷酰转移酶（GALT）和尿苷二磷酸半乳糖-4-表异构酶的联合作用而发生的尿苷二磷酸葡萄糖和尿苷二磷酸半乳糖浓度的调节，可能对确定复合糖缀合物的合成速率很重要。
