Local intrarenal vasoconstrictor-vasodilator interactions in mild partial ureteral obstruction

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Abstract
Micropuncture studies were performed in Munich-Wistar rats with surgically created chronic partial unilateral ureteral obstruction (UUO). Mean values for superficial single nephron (SN)GFR [glomerular filtration rate], total GFR and initial glomerular plasma flow rate (QA) in obstructed kidneys were essentially identical to values in nonobstructed kidneys. Glomerular capillary hydraulic pressure (.hivin.PGC) was significantly higher in obstructed than in nonobstructed kidneys. This increase in .hivin.PGC served to offset the markedly reduced glomerular capillary ultrafiltration coefficient that was also confined to the kidneys ipsilateral to the ureteral obstruction. During infusion of indomethacin or meclofenamate, SNGFR and QA decreased significantly, in association with elevations in arteriolar resistances in obstructed kidneys; such changes were not observed in nonobstructed kidneys. Local intrarenal factors, rather than circulating or systemic factor(s), bring about functional adaptations to partial ureteral obstruction. An indomethacin- and meclofenamate-sensitive vasodilator (presumably prostaglandin) plays a role in antagonizing the effects of a simultaneously acting vasoconstrictor which, although not identified, displayed the functional properties of angiotensin II.