Effect of Chronic and Acute Changes in Sodium Balance on the Urinary Excretion of Prostaglandins E2 and F2α in Normal Man

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Abstract
1. The effects of changes in sodium balance on renal prostaglandins have been hitherto studied mainly in experimental animals and the results have been controversial. In this study the 24 h urinary excretion of prostaglandins E2 and F2α was measured by radioimmunoassay in seven normal subjects under basal conditions and after 5 days of a diet containing 2 excretion (from 769.7 ± 201.6 sem to 1761.3 ± 304.9 ng/24 h, P2α also increased from 1187.0 ± 390.1 to 1435.6 ± 344.6 ng/24 h, but this was not statistically significant. The prostaglandin E2/prostaglandin F2α ratio increased from 0.83 ± 0.2 to 1.52 ± 0.34 (PP2 decreased after 2 h from 142.4 ± 29.9 to 86.7 ± 22.9 ng/h (P2α decreased at a slower rate, from 98.4 ± 18.7 to 37.5 ± 8.8 ng/h at 4 h (P2/prostaglandin F2α ratio returned to control values (0.90 ± 0.17). Plasma renin activity and aldosterone decreased significantly after 2 h (P2 parallel to changes in plasma renin activity and aldosterone. The similar but quantitatively smaller changes in prostaglandin F2α and the inversion of the ratio between the two prostaglandins during sodium deprivation suggest that at least two factors are involved: increased delivery of substrate for prostaglandin synthase and decreased activity of the prostaglandin E2 9-ketoreductase. Prostaglandins probably play an important role in the adaptation of the kidney to changes in sodium balance.