MacLeod R J, Lembessis P, Hamilton J R
Department of Pediatrics, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada.
Am J Physiol. 1992 Jun;262(6 Pt 1):G1021-6. doi: 10.1152/ajpgi.1992.262.6.G1021.
To further elucidate differences in ion transport properties between jejunal crypt and villus cells, we compared the responses of purified cell suspensions to hypotonic stress using electronic cell sizing to evaluate volume changes and 86Rb and 36Cl efflux. After hypotonic swelling, villus enterocytes undergo a regulatory volume decrease (RVD) due to the loss of K+ and Cl- through volume-activated conductances. After 0.6x isotonic challenge in Na(+)-free medium, crypt cells exhibited only partial RVD, with t1/2 congruent to 15 min. The addition of a cation ionophore, gramicidin (0.25 microM), to hypotonically swollen crypt cells caused an accelerated RVD, which was complete with t1/2 congruent to 5 min. Crypt epithelial cells showed no volume-activated 86Rb efflux, but villus enterocytes had an increased rate of 86Rb efflux after hypotonic dilution (P less than 0.001). Gramicidin added to hypotonically diluted crypt cells greatly increased the rate of 86Rb efflux compared with controls. Both villus (30 s; P less than 0.005) and crypt (2 min; P less than 0.001) cells exhibited volume-activated 36Cl efflux in absence of gramicidin. Cl- channel blockers anthracene-9-carboxylate (9-AC, 300 microM) and indanyloxyacetic acid (IAA-94, 100 microM) prevented crypt RVD (P less than 0.001) in the presence of gramicidin. Ouabain (P less than 0.001) or K(+)-free Na(+)-containing medium, but not Ba2+ (5 mM) or quinine (100 microM), prevented crypt partial RVD. We conclude that crypt cells lack volume-activated K+ conductance. The RVD exhibited by crypt cells, although partial, was due to Cl- loss through a volume-activated Cl- conductance and Na+ loss via Na(+)-K(+)-ATPase.
为了进一步阐明空肠隐窝细胞和绒毛细胞之间离子转运特性的差异，我们使用电子细胞大小测量法来评估体积变化以及86Rb和36Cl外流，比较了纯化细胞悬液对低渗应激的反应。低渗肿胀后，绒毛肠上皮细胞由于通过体积激活的电导丢失K+和Cl-而经历调节性体积减小（RVD）。在无Na+培养基中进行0.6倍等渗刺激后，隐窝细胞仅表现出部分RVD，t1/2约为15分钟。向低渗肿胀的隐窝细胞中添加阳离子离子载体短杆菌肽（0.25μM）会导致RVD加速，t1/2约为5分钟时完成。隐窝上皮细胞未表现出体积激活的86Rb外流，但低渗稀释后绒毛肠上皮细胞的86Rb外流速率增加（P<0.001）。与对照组相比，添加到低渗稀释的隐窝细胞中的短杆菌肽大大增加了86Rb外流速率。在没有短杆菌肽的情况下，绒毛（30秒；P<0.005）和隐窝（2分钟；P<0.001）细胞均表现出体积激活的36Cl外流。Cl-通道阻滞剂蒽-9-羧酸盐（9-AC，300μM）和茚满氧基乙酸（IAA-94，100μM）在存在短杆菌肽的情况下阻止了隐窝RVD（P<0.001）。哇巴因（P<0.001）或无K+含Na+培养基，但不是Ba2+（5mM）或奎宁（100μM），阻止了隐窝部分RVD。我们得出结论，隐窝细胞缺乏体积激活的K+电导。隐窝细胞表现出的RVD虽然是部分的，但归因于通过体积激活的Cl-电导丢失Cl-以及通过Na+-K+-ATPase丢失Na+。
