Effects of sodium loading on the renal synthesis of prostanoids in the rat

1. The production of prostaglandin (PG) E2, F2 alpha and thromboxane B2 (TXB2) by isolated glomeruli, cortical tubular suspensions and medullary and papillary slices was measured in normal Long-Evans rats 4, 8 and 14 days after starting on oral Na+ load and the results were compared with those of rats on a normal Na+ intake. 2. In glomeruli, PGE2 decreased at days 4 and 8, and returned to normal at 14 days. PGF2 alpha decreased only at day 4 and TXB2 decreased in all Na+-loaded animals. In cortical suspensions, a transient decrease of PGE2 was observed at day 4. In medullary slices, PGE2 and TXB2 decreased in all experimental periods. In contrast, in papillae, a significant increase of PGE2 was observed with Na+ loading at day 8, but PGF2 alpha and TXB2 did not change consistently. 3. Similar changes were observed in rats with hypothalamic diabetes insipidus (DI rats) Na+ loaded for 4 days, as compared with DI rats on a normal Na+ intake. 4. The results suggest that prostanoids participate in the renal adaptation to an increased Na+ intake, and that this response is relatively independent of the presence of antidiuretic hormone.