Electron microprobe analysis (EMPX) was employed to determine the alterations in intracellular electrolyte concentrations in proximal tubular cells resulting from acute treatment with amphotericin B. Concurrent clearance data confirmed a drop in glomerular filtration rate (GFR) in the rats treated with amphotericin B infusion (1 mg/kg per h) compared to control animals infused with saline (0.69 kO.11 vs 1.27 2 0.08mL/min per 100 g; P