Cooke H J, Dawson D C
Am J Physiol. 1978 Mar;234(3):E257-61. doi: 10.1152/ajpendo.1978.234.3.E257.
Segments of ileum from newborn rabbits were mounted as flat sheets in Lucite chambers and transmural fluxes of Na, Cl, and alanine were measured in the absence of electrochemical potential gradients. In the presence of 140 mM Na, the ileum of the newborn exhibited a serosa-positive electrical PD and a corresponding short-circuit current (Isc) which was markedly enhanced by the addition of D-glucose of L-alanine to the mucosal solution. Alanine-induced increments in Isc were a saturable function of the mucosal alanine concentration. In the presence of Na, alanine was actively absorbed, and the net alanine flux was a saturable function of alanine concentration. When the Na in the bathing solutions was completely replaced by choline, Isc declined to near zero, and the response of Isc to mucosal alanine was abolished. In addition, active amino acid transport was abolished in the absence of Na. In the absence of alanine, the isolated ileum of the newborn actively absorbed Na and Cl, and the algebraic sum of the net movements of these ions accounted for Isc. In the presence of alanine, active Cl transport was abolished and Isc was equal to the net Na absorption. These results indicate that the ileum of the newborn rabbit is similar to that of the adult in its ability to actively absorb Na, Cl, and alanine, but differs from the ileum of the adult by having a greater passive permeability to ions and amino acid, and differs particularly with regard to the effect of mucosal alanine on transmural ion transport.
将新生兔的回肠段制成平片，安装在透明塑料小室中，在不存在电化学势梯度的情况下测量钠、氯和丙氨酸的跨膜通量。在存在140 mM钠的情况下，新生兔回肠表现出浆膜阳性的跨膜电位差（PD）和相应的短路电流（Isc），向黏膜溶液中添加D-葡萄糖或L-丙氨酸可显著增强该电流。丙氨酸诱导的Isc增加是黏膜丙氨酸浓度的饱和函数。在有钠存在的情况下，丙氨酸被主动吸收，净丙氨酸通量是丙氨酸浓度的饱和函数。当浴液中的钠完全被胆碱取代时，Isc降至接近零，且Isc对黏膜丙氨酸的反应消失。此外，在没有钠的情况下，主动氨基酸转运被消除。在没有丙氨酸的情况下，新生兔的离体回肠主动吸收钠和氯，这些离子净移动的代数和构成Isc。在有丙氨酸存在的情况下，主动氯转运被消除，Isc等于净钠吸收量。这些结果表明，新生兔回肠在主动吸收钠、氯和丙氨酸的能力方面与成年兔相似，但在对离子和氨基酸的被动通透性方面与成年兔回肠不同，尤其在黏膜丙氨酸对跨膜离子转运的影响方面存在差异。
