The influence of dietary sodium on urinary prostaglandin excretion

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Abstract
The influence of dietary NaCl urinary excretion of prostaglandins (PG) was studied in unanesthetized female rabbits housed in metabolic cages. Urinary PG levels were determined by radioimmunoassay, bioassay and gas chromatography-mass spectrometry. In the 1st experiment rabbits were fed high (2.5%) and later a low (0.25%) NaCl diet ad lib. A 2- to 5-fold increase in excretion of immunoreactive PGF2.alpha. (iPGF2.alpha.) and iPGE2 was noticed when animals were given the low salt diet. Dietary factors other than NaCl may have contributed to the changes. A 2nd, more controlled, experiment was undertaken. Rabbits were fed 30 g/kg per day of diets differing only in the content of NaCl, 2% and 0.37%, respectively. On the high salt diet the rabbits excreted 0.1 .+-. 0.04 .mu.g/day of PGE2 and 2.0 .+-. 0.5 .mu.g/day of iPGF2.alpha.. After equilibration on the low salt diet the PGE2 excretion rate increased to 1.5 .+-. 0.3 .mu.g/day (P < 0.001) and that of iPGF2.alpha. to 3.4 .+-. 0.4 .mu.g/day (P < 0.01). An inverse relationship may exist between renal excretion and the activity of the renal PG system.