Intracellular elemental concentrations in renal tubular cells. An electron microprobe analysis

In order to be able to examine the processes involved in transepithelial transport in tissues, which are not composed of a single cell type, methods are required, which permit analysis at a cellular level. The technique of electron microprobe analysis permits the intracellular concentrations of many elements to be determined simultaneously in various portions of the cell. The application of this method to renal cortical tissue has shown that the best estimates of the cytoplasmic concentrations are to be obtained in regions close to the nucleus, farthest from the basolateral infoldings and microvilli, which separate the intracellular environment from the extracellular space. The nuclear concentrations of Na and K do not differ from those in the surrounding cytoplasm, although those of P and Cl are somewhat higher in cytoplasm. The intracellular element concentrations in the different cell types vary somewhat, proximal tubular cells contain higher concentrations of Na and Cl and lower ones of P than distal tubular cells. Following ischaemia, a manoeuvre know to result in a disturbance of intracellular electrolytes, Na was observed to rise and K to fall only in the non-surface cells of kidneys exposed to the air, but in all cells, if the kidneys were kept air-free in an atmosphere of N2. The proximal and distal tubular cells showed a variable resistance to ischaemia, the distal tubular cells being much more resistant. Despite the severity of the electrolyte disturbance following ischaemia, the intracellular composition was completely restored one hour after re-introducing renal blood flow.