Effects of bradykinin on renal interstitial pressures and proximal tubule reabsorption

Renal interstitial Starling forces have been postulated as the link between the peritubular microcirculation and fluid reabsorption by the proximal tubule. The renal vasodilator bradykinin was used as a tool to test this relationship in micropuncture studies in the rat. Bradykinin increased peritubular capillary and interstitial hydrostatic pressures and decreased peritubular and interstitial oncotic pressures. The balance of Starling forces in the interstitium (interstitial oncotic pressure minus interstitial hydrostatic pressure) was significantly decreased from 6.5 +/- 2.3 to -4.0 +/- 1.3 mmHg without a change in fluid reabsorption by the proximal tubule. We conclude that renal interstitial Starling forces do not regulate reabsorption by the superficial proximal tubule in the rat in response to bradykinin.