Hydrostatic pressures in peritubular capillaries and tubules in the rat kidney.

FALCHUK, K. H., AND R. W. BERLINER. Hydrostatic pressures in peritubular capillaries and tubules in the rat kidney. Am. J. Physiol. 220(5) : 1422-1426. 197 1 .-A servo pressure-measuring device was used to study the pressure relationships in the tubules and capillaries of the superficial renal cortex by micropuncture techniques. Mean pressure was 10.9 =t 0.5 mm Hg in proximal tubules, 6.5 rt 0.5 mm Hg in peritubular capillaries, 5.5 rfr 0.4 mm Hg in distal tubules, and 13.5 =t 0.8 mm Hg in star vessels. Following infusions of isotonic saline, mannitol, or albumin solutions, or partial constriction of the renal vein, or occlusion of both carotids, the pressures in both proximal tubules and peritubular capillaries increased. Following partial constriction of the aorta, the pressures decreased. The difference in pressure between capillaries and proximal tubules was present under all conditions. These data suggest that the relationship between pressures in the structures of the renal cortex and the interstitial space is complex. It is suggested that renal cortical interstitial pressure is lower than previously believed, and probably no higher than about 5 mm Hg.