von Zglinicki T, Roomans G M
Institute of Pathology, Charité, Berlin, Germany.
Scanning Microsc Suppl. 1994;8:25-34; discussion 34-5.
Cytoplasmic monovalent ion and water contents in morphologically defined mice jejunal cells were measured by X-ray microanalysis in order to gain insight into the cell-type specificity of intestinal electrolyte transport mechanisms. Ion and water contents were measured independently. It was found that in some cases net fluxes of ions and water do not correspond to the assumption of constant osmotic activity of cytoplasmic Na and K ions. Stimulation of secretion with the cholinergic secretagogue pilocarpine resulted in efflux of Cl- from an influx of K+ into crypt enterocytes containing small secretion granula (crypt A cells). No significant changes in ion concentrations were found in crypt enterocytes without secretion granula (crypt B cells). Crypt A cells were more likely to be stimulated by pilocarpine than crypt B cells, and the basolateral K+ efflux pathway in crypt A cells appeared to be rate-limiting. In villus enterocytes, pilocarpine stimulated Cl- efflux. Isoproterenol caused marked changes in the cytoplasmic Cl content of all epithelial cells. These changes were reversed by inhibition of adenylate cyclase by alloxan, with the sole exception of Cl increase in villus absorptive cells. The results are consistent with an cAMP-mediated stimulated secretion in crypt epithelial cells and a predominantly cAMP-independent stimulation of absorption in villus cells. The results obtained suggest a transcellular route of Cl absorption in the mouse jejunum.
为深入了解肠道电解质转运机制的细胞类型特异性，采用X射线微分析法测定形态学明确的小鼠空肠细胞中的细胞质单价离子和水含量。离子和水含量分别进行测定。结果发现，在某些情况下，离子和水的净通量并不符合细胞质中钠和钾离子渗透活性恒定的假设。用胆碱能促分泌剂毛果芸香碱刺激分泌，导致含有小分泌颗粒的隐窝肠上皮细胞（隐窝A细胞）中钾离子流入，氯离子流出。在没有分泌颗粒的隐窝肠上皮细胞（隐窝B细胞）中，未发现离子浓度有显著变化。隐窝A细胞比隐窝B细胞更容易受到毛果芸香碱的刺激，并且隐窝A细胞中的基底外侧钾离子外流途径似乎是限速的。在绒毛肠上皮细胞中，毛果芸香碱刺激氯离子外流。异丙肾上腺素引起所有上皮细胞细胞质中氯离子含量的显著变化。除了绒毛吸收细胞中氯离子增加外，这些变化可被四氧嘧啶抑制腺苷酸环化酶所逆转。结果与隐窝上皮细胞中cAMP介导的刺激分泌以及绒毛细胞中主要不依赖cAMP的吸收刺激一致。所得结果提示小鼠空肠中氯离子吸收的跨细胞途径。
