Nielsen R
Institute of Biological Chemistry A, University of Copenhagen, Denmark.
Acta Physiol Scand. 1987 Oct;131(2):221-9. doi: 10.1111/j.1748-1716.1987.tb08230.x.
The aim of the present investigation was to explore whether in isolated frog skin there should be different pathways for K+ absorption and secretion. Therefore, the unidirectional fluxes of 42K+ and the K+-like isotope 86Rb+ were measured. By using various transport inhibitors, separate pathways for active K+ absorption and secretion were detected. The data obtained indicate that the transepithelial K+ and Rb+ transport across isolated frog skin is made up of four different components: one passive and three active. One of the active components is directed from the apical to the basolateral solution, whereas the other two are in the opposite direction. The direction of the net K+ transport depends on the activities of these three active transport components. The active uptake mechanism, which is present in the epithelial cells, discriminates between K+ and Rb+. The ratio between the K+ and Rb+ influxes, K/Rb, is about 3. The presence of Ba2+, furosemide or ouabain in the apical solution had no effect on the K+ influx. The active secretion of K+ takes place via two different pathways, namely the skin glands and the epithelial cells. The K+ secretion via the glands is inhibited by furosemide (basolateral), but is unaffected by Ba2+ (apical) and does not discriminate between K+ and Rb+. The active K+ secretion via the epithelial cells is blocked by apical Ba2+, and it discriminates between K+ and Rb+. The ratio between the K+ and Rb+ effluxes is about 2. The data presented show that the K+ channels in the apical and the basolateral membrane of the epithelial cells discriminate between K+ and Rb+.(ABSTRACT TRUNCATED AT 250 WORDS)
本研究的目的是探究在离体蛙皮中，钾离子（K⁺）的吸收和分泌是否存在不同途径。因此，测量了⁴²K⁺和钾类似物⁸⁶Rb⁺的单向通量。通过使用各种转运抑制剂，检测到了主动K⁺吸收和分泌的不同途径。所获得的数据表明，经离体蛙皮的跨上皮K⁺和Rb⁺转运由四个不同成分组成：一个被动成分和三个主动成分。其中一个主动成分是从顶端溶液指向基底外侧溶液，而另外两个则方向相反。净K⁺转运的方向取决于这三个主动转运成分的活性。上皮细胞中存在的主动摄取机制能够区分K⁺和Rb⁺。K⁺与Rb⁺流入量的比值K/Rb约为3。顶端溶液中存在Ba²⁺、呋塞米或哇巴因对K⁺流入量没有影响。K⁺的主动分泌通过两种不同途径进行，即皮肤腺体和上皮细胞。通过腺体的K⁺分泌受呋塞米（基底外侧）抑制，但不受Ba²⁺（顶端）影响，且不区分K⁺和Rb⁺。通过上皮细胞的主动K⁺分泌被顶端Ba²⁺阻断，且能区分K⁺和Rb⁺。K⁺与Rb⁺流出量的比值约为2。所呈现的数据表明，上皮细胞顶端和基底外侧膜中的K⁺通道能够区分K⁺和Rb⁺。（摘要截短于250字）
