Effect of spironolactone treatment on the ultrastructure of cortical intercalated cells in the rat kidney.

The ultrastructure of intercalated cells in the rat renal cortex was investigated after 7 days of treatment with the mineralocorticoid inhibitor spironolactone. In untreated and treated animals, two subgroups of IC cells (A-IC and B-IC) could be recognized by electron microscopy, but a substantial fraction of IC cells that corresponded to neither A nor B forms, so-called NonA-NonB, was also found. After spironolactone treatment, qualitative and morphometric analyses showed a decrease in volume density of mitochondria, in cell cross-sectional area, and in boundary length of basolateral membranes in A-IC cells. Among the NonA-NonB-IC cells, some revealed especially abundant mitochondria. Although the frequency of NonA-NonB-IC cells did not change significantly, these mitochondria-rich cells appeared with increased frequency after spironolactone treatment. The ultrastructural changes in A-IC cells might reflect a direct effect of spironolactone on the A-IC cells. However, it is also conceivable that the changes are secondary to functional alterations induced in neighboring segment-specific cells by the experimental conditions.