Miller D L, Hamburger S A, Schedl H P
Am J Physiol. 1979 Oct;237(4):E389-96. doi: 10.1152/ajpendo.1979.237.4.E389.
We examined effects of luminal osmolality on net water and solute movements in rat duodenum and ileum. Solutions of sodium chloride (permeating solute) or mannitol (nonpermeating solute) at hypo-, iso-, or hyperosmotic concentrations were recirculated through in situ segments. Luminal osmolality increased towards that of plasma with hyposmotic solutions of both solutes. With isosmotic solutions, luminal osmolality did not change with sodium chloride, but increased with mannitol. With hyperosmotic solutions, luminal osmolality always decreased toward that of plasma with sodium chloride; with mannitol, however, decreases were significant only when initial concentrations were above 400 mosmol/kg. The decrease in osmolality of hyperosmotic sodium chloride resulted from sodium absorption and water secretion. Thus, both hypo- and hyperosmotic solutions of sodium chloride adjusted toward isomolality with plasma by the usual mechanisms of water and solute movement. With mannitol, however, osmotic adjustment of hypertonic luminal contents was restricted or even absent due to movement of sodium down its concentration gradient and reduced hydraulic conductivity of the gut.
我们研究了管腔渗透压对大鼠十二指肠和回肠中水和溶质净移动的影响。将低渗、等渗或高渗浓度的氯化钠溶液（可渗透溶质）或甘露醇溶液（不可渗透溶质）通过原位肠段进行循环。两种溶质的低渗溶液均可使管腔渗透压向血浆渗透压升高。使用等渗溶液时，氯化钠溶液不会改变管腔渗透压，但甘露醇溶液会使其升高。使用高渗溶液时，氯化钠溶液会使管腔渗透压始终向血浆渗透压降低；然而，对于甘露醇溶液，仅当初始浓度高于400 mosmol/kg时，渗透压降低才显著。高渗氯化钠溶液渗透压的降低是由于钠的吸收和水的分泌。因此，氯化钠的低渗和高渗溶液通过水和溶质移动的常规机制向与血浆等渗的方向调节。然而，对于甘露醇溶液，由于钠沿其浓度梯度移动以及肠道水力传导率降低，高渗管腔内容物的渗透调节受到限制甚至不存在。
