Spironolactone-induced inhibition of aldosterone biosynthesis in primary aldosteronism: morphological and functional studies.

Twenty-five patients harboring aldosterone-producing adenomas were treated with spironolactone for 2-170 days immediately preoperatively. In the early period of administration of the drug (up to 27 days), plasma and urinary aldosterone decreased sharply while plasma renin activity (PRA) and serum potassium were rising. During this period of time, spironolactone bodies (SB), which form exclusively in cells actively producing aldosterone, were forming rapidly in the tumor cells but not in the inactive glomerulosa cells proper. The SB appear to be a morphological expression of a block in aldosterone biosynthesis. Since SB do not occur in normal fasciculata cells, which, like glomerulosa cells, also synthesize corticosterone, it is concluded that spironolactone inhibition of aldosterone biosynthesis occurs between corticosterone and aldosterone. Recent studies in vitro by others have suggested that the inhibition occurs at the corticosterone-methyl oxidase step, I (Ulick’s nomenclature). The great diuresis of sodium and retention of potassium resulting from continued administration of the drug sharply activates aldosterone stimulatory factors. Aldosterone production may return to baseline levels in several weeks but it is inappropriately low in relation to the levels of PRA and serum potassium. With the further passage of time (average 4-6 wk), aldosterone production may increase 50%-100% above baseline levels, suggesting that the block has disappeared or is receding. At this time SB are diminishing in number and by 170 days of the drug they have virtually disappeared. We have hypothesized, among other possibilities, that recovery of the ability to convert corticosterone to aldosterone occurs by virtue of a mechanism activated by sodium deficiency, independent of angiotensin, which stimulates step 1 of the corticosterone-methyl oxidase system. As the block in the final step(s) of the biosynthetic pathway recedes, the existing elevated levels of angiotensin become much more effective in stimulating the production of aldosterone.