AJP - Renal Physiology, Vol 248, Issue 1 43-F47, Copyright © 1985 by American Physiological Society
Aldosterone-stimulated transmethylations are linked to sodium transport
W. P. Wiesmann, J. P. Johnson, G. A. Miura and P. K. Chaing
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(-7)
M) 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 carboxy-methylation were inhibited by DZA. DZA (300 microM) caused
a mild decrease in basal short-circuit current (ISC) but completely
inhibited the ISC response to 10(-7) 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
methylation, protein carboxymethylation, and turnover of PC from choline.
Inhibition of methylation reactions coincides with the inhibition of ISC
response to Aldo.
