Sodium intake as a determinant of urinary prostaglandin excretion. Studies in the brattleboro rat

In order to investigate the effects of changes in sodium (Na) balance on the renal production of prostaglandins (PG) E ₂ and F_2α in the absence of antidiuretic hormone (ADH),studies were performed in Brattleboro rats, without endogenous ADH, and in heterozygote Long Evans rats which served as controls. All rats received a diet virtually devoid of Na, with distilled water ad libitum,and Na intake was modified by adding different quantities of Na to the drinking water. Three groups were studied for each strain: normal Na intake,low Na intake and Na loading. At the end of a 14 day diet period urinary PGE ₂ and PGF_2α were measured by radioimmunoassay in collections obtained for three consecutive days. In the Na depletedanimals, both PGE₂ = and PGF_2α decreased. The PGE₂ PGF_2α ratio (E/F ratio) was unchanged. In contrast, Na loading induced a significant decrease of PGE₂ but PGF_2α increased,thouqh notsignificantly. The E/F ratio was significantly decreased. The results were qualitatively similar in the presence or absence of ADH, but the Brattleboro rats, overall, excreted less PGs than controls. The results suggest that changes in Na balance are major factors influencing urinary PG excretion. These substances probably play a role in the modifications of Na handling by the kidney in different balance states.