Hanrahan J W, Phillips J E
Department of Zoology, University of British Columbia, Vancouver, B.C.Canada.
J Exp Biol. 1984 Jul;111:201-23. doi: 10.1242/jeb.111.1.201.
The kinetics of (36)C1 fluxes across cAMP-stimulated, short-circuited locust rectum were studied. Raising external K(+) from 0 to 100 mM increased both K(t) and V(max) for net Cl transport (J(CI)net) by four- to six-fold. Hill plots of J(CI)net indicated non-cooperative Cl interactions. The sequence for cation stimulation of J(CI)net was K > Rb > Cs > Na > NH4 . Low levels of K were stimulatory only when added to the mucosal side. Cyclic AMP (cAMP) caused a small active absorption of K, although this was minor compared to the four fold increase in transepithelial K diffusion (Pk). Neither cAMP stimulation of J(K)net nor of Pk was sensitive to Cl removal, suggesting that K-stimulated Cl absorption and K transport are not mediated by the same co-transport mechanism. Potassium is the counter-ion for electrogenic Cl transport because J(K)net was less than 10% of the J(CI)net during cAMP exposure under Isc conditions, but J(K)net equalled J(CI)net at open-circuit.
研究了经环磷酸腺苷（cAMP）刺激的短路蝗虫直肠中³⁶Cl通量的动力学。将外部钾离子（K⁺）浓度从0 mM提高到100 mM，使净氯转运（J(CI)net）的K(t)和V(max)均增加了四至六倍。J(CI)net的希尔图表明氯的相互作用是非协同性的。阳离子对J(CI)net刺激作用的顺序为K > Rb > Cs > Na > NH₄ 。低水平的钾只有添加到黏膜侧时才具有刺激作用。环磷酸腺苷（cAMP）引起少量钾的主动吸收，尽管与跨上皮钾扩散（Pk）增加四倍相比，这一吸收量较小。cAMP对J(K)net或Pk的刺激作用均对氯的去除不敏感，这表明钾刺激的氯吸收和钾转运不是由相同的共转运机制介导的。钾是电生性氯转运的抗衡离子，因为在短路电流（Isc）条件下，cAMP暴露期间J(K)net小于J(CI)net的10%，但在开路时J(K)net等于J(CI)net。
