Cooke H J, Cooke A R
Am J Physiol. 1982 Apr;242(4):G308-12. doi: 10.1152/ajpgi.1982.242.4.G308.
The effect of tryptophan on sodium and chloride fluxes was determined simultaneously on paired flat-sheet preparations of newborn rabbit jejunum under short-circuit conditions. In the absence of amino acids, the newborn rabbit jejunum actively absorbed sodium, and possibly bicarbonate, whereas chloride appeared to be distributed passively across the jejunum. Tryptophan (2 mM) caused an increment in short-circuit current (Isc) that was due to an increase in net active sodium flux and had no significant effect on tissue conductance. At a 10 mM concentration, tryptophan initially increased Isc, although not to as large a degree as phenylalanine or alanine, and then caused a progressive decline that reached a plateau around 60 min. The reduction in Isc was attributed primarily to abolition of sodium absorption and stimulation of chloride secretion. Tryptophan reduced the unidirectional fluxes of sodium, increased those of chloride, and decreased total tissue conductance. These results suggest that 10 mM tryptophan initially causes a predicted increase in sodium absorption, followed by an inhibition of sodium absorption and stimulation of chloride secretion. The mechanism of action of tryptophan resulting in changes in ion fluxes is unknown.
在短路条件下，同时测定色氨酸对新生兔空肠成对平板制剂中钠和氯通量的影响。在缺乏氨基酸的情况下，新生兔空肠主动吸收钠，可能还吸收碳酸氢根，而氯似乎是被动地分布于整个空肠。色氨酸（2 mM）使短路电流（Isc）增加，这是由于净主动钠通量增加所致，且对组织电导无显著影响。在10 mM浓度时，色氨酸最初增加了Isc，尽管增幅不如苯丙氨酸或丙氨酸大，随后导致其逐渐下降，并在约60分钟时达到平稳状态。Isc的降低主要归因于钠吸收的消除和氯分泌的刺激。色氨酸减少了钠的单向通量，增加了氯的单向通量，并降低了组织总电导。这些结果表明，10 mM色氨酸最初会导致钠吸收如预期那样增加，随后抑制钠吸收并刺激氯分泌。色氨酸导致离子通量变化的作用机制尚不清楚。
