Pressures in static and dynamic states from capsules implanted in the kidney.

OTT, C. E., L. G. NAVAR, AND A. C. GUYTON. Pressures in static and dynamic states from capsules implanted in the kidney. Am. J. Physiol. 22 l(2) : 394-400. 197 1 .-Renal interstitial fluid pressure was measured in 35 unanesthetized dogs from perforated capsules implanted in the kidney. Pressure measurements were made from a small catheter run from the interior of the capsule to the exterior of the animal. Measurements were made approximately every 3 days for a period of up to 80 days. The average pressure obtained in over 150 measurements was 6.0 & 0.52 mm Hg (SEM). These results indicate that the renal interstitial fluid pressure is lower than previously suggested by other methods. Acute experiments were performed in 24 animals in which a) renal arterial pressure was altered, b) renal venous pressure was increased, c) ureteral pressure was increased, or d) 1.0 M mannitol was infused. The renal interstitial fluid pressure changed in response to all of the above stimuli. The effects on the renal interstitial fluid pressure caused by ureteral pressure or venous pressure changes were over 10 times as great as those caused by a similar change in arterial pressure. The possibility is discussed that changes in renal arterial pressure, renal venous pressure, and ureteral pressure, as well as infusion of osmotic diuretics, can affect the overall balance of forces across the tubular wall in part through their effects on renal interstitial fluid pressure.