Renal prostaglandin E2 synthesis in the Brattleboro homozygous diabetes insipidus rat.

The effect of vasopressin (VP) on prostaglandin (PG) synthesis in the renal collecting tubule remains equivocal. To further address this issue, the present study determined the effects of chronic absence of VP on renal medullary collecting tubule PG synthesis. Prostaglandin E2 (PGE2) synthesis was measured in both inner and outer medullary slices and collecting tubules microdissected from the inner medulla (PCD) and outer medulla (MCT) of Brattleboro homozygous diabetes insipidus (DI) rats, which are genetically devoid of VP, and from Long Evans (LE) control rats. In vitro PGE2 synthesis was significantly lower in both inner medullary (delta - 56%; p less than 0.001) and outer medullary (delta - 56%; p less than 0.01) slices of DI rats compared to controls. Vasopressin tannate treatment (0.5 U/day for 5 days) increased urinary PG excretion, and increased in vitro PGE2 synthesis in both inner and outer medullary slices of DI rats to levels that did not differ from vehicle-treated LE controls. In contrast, PGE2 synthesis in both PCD and MCT of DI rats did not differ from LE controls when incubated either in an isotonic (300 mOsm) medium, or in an hypertonic (1000 mOsm) medium. These results suggest that PGE2 biosynthetic capacity of medullary collecting tubules in the DI rat is not dependent on VP, while depressed PGE2 synthesis in renal medullary slices of DI rats, suggests that the interstitial cell is the primary medullary site of PG synthesis which is modulated by VP.