Electron microprobe analysis of intracellular elements in the rat kidney

Abstract

The concentrations of intracellular elements were determined by electron microprobe analysis in the nucleus and cytoplasm of freeze-dried cryosections of superficial proximal and distal tubules of the rat kidney. For the nucleus of the proximal tubular cell, the concentrations of sodium and chloride were 20 and 23 mmoles/kg of wet wt, and those of potassium and phosphorus were 144 and 150 mmoles/kg wet wt. For the nucleus of the distal tubular cell, the concentrations of sodium and chloride were significanlty lower (11 and 13 mmoles/kg wet wt), that of potassium was unchanged (143 mmoles), and that of phosphorus was significantly higher (175 mmoles). Towards the basolateral infoldings of the proximal and distal tubules and the brush border of the proximal tubules, the concentrations of sodium and chloride were higher and those of potassium and phosphorus were lower than those obtained in the nucleus, indicating the presence of extracellular compartments in these regions. Measurements performed in the centrally located cytoplasm of proximal and distal tubular cells, close to the nucleus, showed sodium and potassium concentrations to the indistinguishable from those in the nucleus, whereas chloride and phosphorus concentrations were considerably higher. These data demonstrate differences in the intracellular concentrations of phosphorus, sodium, and chloride between proximal and distal tubular cells. In neither the proximal nor the distal tubular cells, however, could a concentration difference for sodium and potassium between nucleus and cytoplasm be determined.

Fluorescent imaging of Cl - in Amphiuma red blood cells: How the nuclear exclusion of Cl - affects the plasma membrane potential

“…With electron microprobe analysis, maturating chick red blood cells (18 day, near hatching) had N͞C ratios ϭ 0. 48 (44); for rat renal tubular cells, the N͞C ratios for Cl Ϫ and Na ϩ varied somewhat depending on the cytoplasmic region analyzed (45,46); and in rat hepatocytes, where N͞C ϭ 0.9 for Cl Ϫ and 1.1 for Na ϩ (47). It is evident that in all of these studies, there are only small variations in N͞C values for Cl Ϫ and Na ϩ .…”

Quantitative Morphology of Renal Cortical Structures during Compensatory Hypertrophy

“…Small areas (1–2 µm 2 ) were scanned for 100 s and the emitted X-rays analyzed in the energy range of 0.2–20 keV. Measurements were restricted to the cell nucleus in order to avoid ‘contamination’ by basolateral infoldings and apical vesicles with electrolyte concentrations differing from cyto- and nucleosol [14, 15]. …”

Na+-induced inward rectification in the two-pore domain K+channel, TASK-2

“…The resting membrane potential of the rabbit proximal tubule depolarizes transiently, from a resting value of around Ϫ40 to Ϫ25 mV on exposure to the Na ϩ -cotransported substrate alanine (15). Thus the basolateral membrane potential and intracellular Na ϩ , at least in rabbit proximal tubule, enter the range where channel block may be apparent; using the above "worst-case" values; i.e., at an intracellular Na ϩ of 62 mM and voltage of Ϫ25 mV, one would predict, using the Woodhull equation, a 21% block of TASK2 currents by intracellular Na ϩ ; if the Na concentration were lower, e.g., 20 mM as in the rat (2,34), this inhibition would be reduced to 9%. Certainly, before washout in the CHO cells used in the current study, rectification was apparent at almost all potentials positive to the reversal potential (Fig.…”