Brodin B, Nielsen R
Laboratory of Biological Chemistry A, August Krogh Institute, University of Copenhagen, Denmark.
Pflugers Arch. 1993 Jun;423(5-6):411-7. doi: 10.1007/BF00374935.
The aim of the present study was to investigate the effects of small, unilateral changes in solution osmolarity on active sodium transport and cellular electrophysiological parameters in frog skin. The active sodium transport across the skin was measured as the amiloride-sensitive short-circuit current (Isc) and cellular potential was monitored with microelectrodes, while small (+/- 20 mOsm) osmotic gradients were imposed on the skin. Increasing the osmolarity of the apical bathing solution (or decreasing the osmolarity of the basolateral solution) increased ISC, lowered tissue resistance (R), depolarized the cellular potential and decreased the fractional resistance of the apical membrane, which indicates an increased apical sodium permeability. Conversely, a similar increase in basolateral osmolarity (or a decrease in apical osmolarity) lowered the Isc, increased R, hyperpolarized the cells and increased the fractional resistance of the apical membrane, indicating a decrease in apical sodium permeability. The results indicate that the osmotic gradient across the skin, rather than solution osmolarity as such, is responsible for the observed changes in Isc and apical sodium permeability after small osmotic perturbations.
本研究的目的是探究溶液渗透压的微小单侧变化对蛙皮中钠主动转运及细胞电生理参数的影响。通过测量阿米洛利敏感的短路电流（Isc）来测定经皮肤的钠主动转运，并用微电极监测细胞电位，同时在皮肤上施加微小（±20 mOsm）的渗透梯度。增加顶端浸浴溶液的渗透压（或降低基底外侧溶液的渗透压）会使Isc升高、组织电阻（R）降低、细胞电位去极化，并降低顶端膜的分数电阻，这表明顶端钠通透性增加。相反，基底外侧渗透压的类似增加（或顶端渗透压的降低）会使Isc降低、R增加、细胞超极化，并增加顶端膜的分数电阻，表明顶端钠通透性降低。结果表明，跨皮肤的渗透梯度而非溶液渗透压本身，是造成微小渗透扰动后Isc和顶端钠通透性出现观测变化的原因。
