Holman G D, Naftalin R J
Biochim Biophys Acta. 1975 Mar 13;382(2):230-45. doi: 10.1016/0005-2736(75)90181-9.
Unidirectional fluxes of D-galactose across the brush and serosal border of rabbit ileum were determined using the method described previously (Naftalin, R. J. and Curran, P.F. (1974) J. Membrane Biol. 16, 257-278). With ringer [Na] equals 75 meguiv., the Km for galactose influx across the brush-border is 5mM, with 0.1 mM ouabain present K-m equals 50 mM, the V (2.0 munol - CM-2-H-1) remains unaltered. The Michaelis parameters for galactose influx across the serosal border are K-m equals 59 plus or minus 9 mM and V equals 4.7 plus or minus 0.24 mumol-cm-2-h-1 and for efflux K-m equals 85 plus or minus 10 mM and V equals 6.8 plus or minus 0.7 mumol-CM-2-H-1. 2. 2-Deoxy-D-glucose and methyl beta-D-glucopyranoside inhibit galactose entry exclusively at the serosal and mucosal borders respectively, while 3-O-methyl-D-glucose inhibits galactose influx at both borders. 0.1 mM ouabain increases the K1 of 3-O-methylglucose for the serosal transport system (100 mM) is unaffected by ouabain. Inhibition of mucosal galactose transport by ouabain or by competition with other sugars results in a reciprocal increase in exit permeability and decrease in entry permeability. Inhibition of serosal galactose transport results in inhibition of both the entry and exit permeability, entry is more affected. 3. There is a small degree of permeability asymetry at the serosal border to galactose which is reduced by ouabain or removel of Na+ from the Ringer. Uptake of 14C-labelled galactose from the serosal solution into the tissue is also inhibited by addition of ouabain or Na+ removal. It is therefore considered that there is a weak active transport system for galactose at the serosal border. 4. Net transepithelial galactose flux is sufficiently high and serosal permeability to galactose sufficiently low to be consistent with the view that galactose is concentrated within the tissue fluid, after conviction (Naftalin, R.J. and Holman, G.D. (1974) Biochim. Biophys. Acta., 373, 453-470) across the mucosal border because it is reflected at the serosal boundary.
采用先前描述的方法（Naftalin, R. J. 和Curran, P.F. (1974) J. Membrane Biol. 16, 257 - 278）测定了D - 半乳糖在兔回肠刷状缘和浆膜缘的单向通量。在林格液中[Na]等于75 mequiv.时，半乳糖跨刷状缘流入的Km为5mM，存在0.1 mM哇巴因时K - m等于50 mM，V（2.0 μmol·cm⁻²·h⁻¹）保持不变。半乳糖跨浆膜缘流入的米氏参数为K - m等于59 ± 9 mM，V等于4.7 ± 0.24 μmol·cm⁻²·h⁻¹，流出的K - m等于85 ± 10 mM，V等于6.8 ± 0.7 μmol·cm⁻²·h⁻¹。2. 2 - 脱氧 - D - 葡萄糖和甲基 - β - D - 吡喃葡萄糖苷分别仅在浆膜和黏膜边界抑制半乳糖进入，而3 - O - 甲基 - D - 葡萄糖在两个边界均抑制半乳糖流入。0.1 mM哇巴因增加了3 - O - 甲基葡萄糖对浆膜转运系统的K1（100 mM）不受哇巴因影响。哇巴因或与其他糖类竞争对黏膜半乳糖转运的抑制导致流出通透性的相应增加和进入通透性的降低。对浆膜半乳糖转运的抑制导致进入和流出通透性均受到抑制，进入受影响更大。3. 在浆膜边界对半乳糖存在小程度的通透性不对称，哇巴因或从林格液中去除Na⁺可使其降低。从浆膜溶液向组织中摄取¹⁴C标记的半乳糖也受到哇巴因添加或Na⁺去除的抑制。因此认为在浆膜边界存在一个弱的半乳糖主动转运系统。4. 净跨上皮半乳糖通量足够高，且浆膜对半乳糖的通透性足够低，这与半乳糖在穿过黏膜边界后（Naftalin, R.J. 和Holman, G.D. (1974) Biochim. Biophys. Acta., 373, 453 - 470）在组织液中被浓缩的观点一致，因为它在浆膜边界被反映出来。
