Armbrecht H J, Wasserman R H
J Nutr. 1976 Sep;106(9):1265-71. doi: 10.1093/jn/106.9.1265.
In previous experiments, lactose was shown to increase the absorption of Ca++ by the small intestine of the rat and other mammals. To further investigate the mechanism of the lactose effect, Ca++ uptake was studied in everted gut sac preparations. Gut sacs from the rat ileum were preincubated with or without lactose for 45 minutes, and then the tissue uptake of 45Ca over the first 3 minutes was measured in the presence or absence of lactose. The presence of 160 mM lactose increased the initial rate of Ca++ uptake in the first minute by 64% compared to the NaCl control. The lactose effect was dependent on the presence of lactose in the preincubation medium only and not on the presence of lactose during the measurement of Ca++ uptake. Lactose increased Ca++ absorption when the Ca++ concentrations ranged from 0.1 to 10 mM. However, the magnitude of the enhancement was dependent on the lactose concentration and was reduced below 160 mM lactose. When Ca++ and lactose uptake during a 45 minute period was measured in parallel experiments, no evidence for the co-transport of lactose and Ca++ into the tissue was found. These and other data indicated that lactose is not interacting directly with Ca++ in solution but is interacting with the absorptive cells of the intestine to increase their permeability to Ca++.
在先前的实验中，已证明乳糖可增加大鼠和其他哺乳动物小肠对Ca++的吸收。为了进一步研究乳糖作用的机制，在外翻肠囊制剂中研究了Ca++的摄取情况。将来自大鼠回肠的肠囊在含或不含乳糖的条件下预孵育45分钟，然后在有或无乳糖存在的情况下测量最初3分钟内45Ca的组织摄取量。与NaCl对照相比，160 mM乳糖的存在使第一分钟内Ca++摄取的初始速率提高了64%。乳糖的作用仅取决于预孵育培养基中乳糖的存在，而不取决于Ca++摄取测量期间乳糖的存在。当Ca++浓度在0.1至10 mM范围内时，乳糖增加了Ca++的吸收。然而，增强的幅度取决于乳糖浓度，在低于160 mM乳糖时会降低。在平行实验中测量45分钟内Ca++和乳糖的摄取时，未发现乳糖和Ca++协同转运进入组织的证据。这些以及其他数据表明，乳糖并非在溶液中直接与Ca++相互作用，而是与肠道的吸收细胞相互作用，以增加其对Ca++的通透性。
