Prostaglandin-dependent changes in renal haemodynamics and excretory patterns before and after release of 24 hours bilateral ureteral ligation

In the anesthetized dog during and 1 hr after release of 24 h bilateral ureteral ligation (BUL) renal blood flow (RBF) decreased to 44 and 51%, respectively, as compared with normal controls. After release there was a marked increase in sodium and water excretion, so-called postobstructive diuresis (POD), in spite of a considerably reduced glomerular filtration rate (GFR). Radioactive microspheres revealed a proportionate decrease of perfusion in all cortical layers before, and inward shifting after release of the ligature. Inhibition of intrarenal prostaglandin (PF) synthesis by indomethacin (IM) before release of BUL led to a further pronounced decrease in RBF both in the pre- and postrelease phases, characterized by a proportionate decrease of perfusion in all cortical layers. Fractional excretion of sodium and water remained moderately increased in spite of a very pronounced hypofiltration. It is assumed that, in contrast to PG-dependent changes in renal haemodynamics due to BUL, enhanced sodium and water excretion (POD) are due to a PG-independent mechanism, most probably to some natriuretic substance produced and/or accumulated during 24 h complete retention.