Effects of 24-hour unilateral ureteral obstruction on glomerular hemodynamics in rat kidney

Abstract

Glomerular hemodynamics were studied, by micropuncture, in Munich-Wistar rats submitted to 24-hour unilateral ureteral ligation (UUL). Glomerular capillary pressure (P(G)), intratubular pressure (P(T)) 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 concentration. SNGFR was both measured by conventional micropuncture techniques and calculated from efferent arteriole blood flow (EABF) and SNFF. Afferent arteriole blood flow (AABF) and resistance of afferent (R(a)) and efferent (R(e)) arterioles were calculated. Measurements were repeated 1 to 2 hours after the release of the ureter. Sham-operated rats were used as control. UUL caused a marked increase in R(a) (from 4.9 ± [SD] 2.4 to 12.7 ± 5.1 dynes/sec/cm-5). The fall in SNGFR (from 111.9 ± [SD] 23.9 to 34.4 ± 23.1 nl/min/kg body wt) was secondary to a decrease in both P(G) and AABF. A further increase in R(a) (16.0 ± 6.7 dynes/sec/cm-5) occurred after releasing the ureter. SNGFR, however, was unaltered (33.7 ± 16.6 nl/min/kg body wt) since P(G) decreased parallel to P(T), but AABF did not significantly change. Conclusion. Ureteral obstruction determines, in 24 hours, a marked cortical ischemia that is not promptly reversed by ureteral release.