Prostaglandin synthesis inhibitors and vasa recta erythrocyte velocities in the rat.

Vasa recta erythrocyte velocities (VRBC) in the exposed renal papilla of anesthetized water-loaded rats were determined before and 60 min after intravenous administration of a prostaglandin synthesis inhibitor (indomethacin, meclofenamate) or the inhibitor vehicle alone. The change in VRBC of ascending and descending vasa recta for the inhibitor group [-17 +/- 5% (SE)] was different from that for controls (+12 +/- 4%, P less than 0.002). Erythrocyte velocities were also determined in vasa recta of antidiuretic rats before and 30 min after administration of indomethacin or vehicle alone. Prostaglandin synthesis inhibition was again associated with a significant decrease in VRBC compared with control (-24 +/- 4% vs. +28 +/- 20%, respectively, P less than 0.025). These findings suggest that prostaglandins play a similar role in regulating blood flow in the renal medulla in water diuresis and antidiuresis.