Aldosterone-Stimulated Transmethylations are Linked to Sodium Transport

摘要

The effect of aldosterone (Aldo) on phospholipid (PL) biosynthesis in cultured toad bladder epithelial cells was studied in cells incubated with (1,2-14C) choline and (methyl-3H) methionine over a 5-h period. Aldo 10 to the minus 7th power did not alter the uptake of either precursor but significantly stimulated the incorporation of both labels into phosphatidylcholine (PC), the only PL labeled. 3H labeling of PC increased 29% and 14C incorporation into PC increased 34% in cells exposed to Aldo. A similar 30% increase in protein carboxymethylation occurred in cells treated with Aldo. 3-Deazaadenosine (DZA), a methylation inhibitor, abolished the Aldo-stimulated increase in PC labeling from 3H methionine. PC labeling from (1,2-14C) choline was not affected by DZA. Basal and Aldo-stimulated protein carboxymethylation were inhibited by DZA. DZA (300 uM) caused a mild decrease in basal short-circuit current (Isc) but completely inhibited the Isc response to 10 to the minus 7th power M Aldo. Inhibition was complete when DZA was added up to 2 h following exposure to Aldo, and was reversible. Cells previously exposed to Aldo showed a significant increase in Isc within 2 h following removal of DZA. We conclude that Aldo stimulates PL mehtylation, protein carboxymethylation, and turnover of PC from choline, Inhibition of methylation reactions coincides with the inhibition of the Isc response to Aldo.