Glomerular hemodynamics were studied, by micropuncture, in Munich-Wistar rats submitted to 24-hour bilateral ureteral ligation (BUL). Glomerular capillary pressure (PG), intratubular pressure (PT), and pressure in the first order peritubular capillaries (EAP) were measured with a servonulling device. Single nephron filtration fraction (SNFF) was calculated from arterial and peritubular blood protein concentrations. Single nephron glomerular filtration rate (SNGFR) was both measured by conventional micropuncture techniques and calculated from efferent arteriole blood flow and SNFF. Afferent arteriole blood flow (AABF) and resistance of afferent (Ra) and efferent (Re) arteriole were calculated. Measurements were repeated in the left kidney after releasing the ureter. Sham operated rats were used as control. BUL caused a fall in SNGFR (from 101.8 +/- 9.7 to 40.7 +/- [SEM] 6.0 nl/min/kg body wt), accounted for by a rise in PT (from 14.1 +/- 0.7 to 28.9 +/- 3.1 mm Hg), glomerular hemodynamics (particularly PG and AABF) being unchanged. A marked increase in Ra (from 6.6 +/- 0.7 to 10.8 +/- 1.5 dynes. sec. cm-5) occurred after releasing the ureter, lessening both PG and AABF. Therefore, a low SNGFR was maintained despite the concomitant normalization of PT.