Whole kidney volume/pressure relationships

Abstract

We measured changes in kidney volume and intrarenal pressure produced by step-wise, steady state increases and decreases in ureteral pressure (UP). The purpose of such maneuvers, termed exercises, was to examine the relationship between changes in kidney volume and the changes in intrarenal pressure responsible for those in kidney volume. Changes in kidney volume were assessed from directly measured changes in kidney weight. Changes in the intrarenal pressure distending the renal capsule (renal subcapsular pressure [RSCP]) were measured by a strain guage diaphragm-type microtransducer placed between cortex and capsule. We measured these whole kidney volume/pressure events before and after saline loading and examined their relationship to changes in renal function following saline loading. We found that after four "exercises", the kidney became more complaint, i.e., occupied a larger volume at any given UP or RSCP, and that the compliance of the kidney was further increased following saline loading. However, about one hour after saline loading, RSCP returned to or below pre-saline loading levels and renal volume returned to pre-saline loading levels; nevertheless, the natriuresis persisted. Thus, an increase in renal volume is not necessary to sustain increased sodium and water excretion in post-saline loading. Finally, we found evidence that the renal capsule provides the major force opposing expansion of outer cortex when intrarenal pressure is increased.

Effects of Albumin and Mannitol on Blood Flow Autoregulation in Isolated Dog Kidneys

“…SCRP closely fol lows changes in proximal intratubular pres sure and renal venous wedge pressure. Thus, SCRP is an index of intrarenal tubular and peritubular capillary pressures [14]. In con trol periods, renal subcapsular pressure was 0 mm Hg at perfusion pressures below the autoregulatory range.…”

“…SCRP reflects the 'total tissue pressure* [12] exerted by the superficial renal cortex on the renal capsule [14]. SCRP closely fol lows changes in proximal intratubular pres sure and renal venous wedge pressure.…”

“…The transected end of the renal vein was always open to the at mosphere. A diaphragm-type strain-gauge micro transducer was used to measure subcapsular renal pressure (SCRP) for quantitative assessment of to tal renal tissue pressure, as described by Hebert et al [14]. The temperature of the perfusate was maintained at 37 °C by passage of the blood through a coil immersed in a constant temperature water bath.…”

Electrical properties of the rabbit cortical collecting duct from obstructed kidneys after unilateral ureteral obstruction. Effects of renal decapsulation.

“…These findings suggest that the effects of renal decapsulation on transport properties observed in CD cells from UUO animals might occur as a result of partial blocking of increased renal pressure, although we did not measure the renal interstitial hydrostatic pressure in control and UUO rabbits before and after renal decapsulation. This is based on the report of Hebert et al (28) that the renal capsule provides the major force opposing expansion of renal cortex in dogs when intrarenal pressure is increased. This is also supported by the report of Hartupee et al (29) that renal decapsulation can partially block the elevations in renal interstitial hydrostatic pressure associated with acetylcholine-induced vasodilation in dogs.…”

“…It has been reported that the renal capsule provides the major force opposing expansion of renal cortex when intrarenal pressure is increased (28). It has been demonstrated in dogs that renal decapsulation partially blocks increases in renal interstitial hydrostatic pressure associated with acetylcholine-induced vasodilation (29).…”