Disproportionate inhibition of sodium reabsorption in the unilaterally diseased kidney of dog and man after an acute saline load

Abstract

A B S T R A C T Clearance studies were performed on 49 split-bladder dogs with a unilateral pyelonephritic or remnant kidney and three patients with unilateral kidney disease to examine the effects of an acute saline load on the diseased kidney (DK) as opposed to a simultaneously studied, contralateral control kidney (CK), which also served to maintain a nonuremic environment.Before saline loading, base line studies in many of the dogs and the three humans were in agreement with previously published data. However, in dogs with a severe pyelonephritic lesion, a greater difference in DK vs. CK fractional excretion of sodium (FEN.) and water was noted, whose magnitude was inversely correlated with the level of glomerular filtration rate (GFR) and maximum urine osmolality of DK compared to CK.An acute saline load (75 ml/kg) resulted in an inhibition of fractional sodium and water reabsorption in the diseased dog kidney which was disproportionately greater than in the simultaneously studied CK, regardless of the type or severity of the lesion. While mean DK GFR for all dogs increased 15% more than CK GFR, failure of FENa to increase after induction of a disproportionate increase in DK GFR with parathyroid hormone suggested that the saline-induced disproportionate increase in GFR was not solely responsible for the exaggerated inhibition of fractional sodium and water reabsorption in the diseased dog kidney. Studies in the three patients after saline loading (25 ml/kg)

Functional adaptation of nephrons in dogs with acute progressing to chronic experimental glomerulonephritis.

“…In addition, maximum tubular secretion of PAH per GFR was similar for both the APGN and intact kidney, also in contrast to the group I studies. These results for the group II studies are similar to those reported for the unilateral pyelonephritic and chronic glomerulonephritic dog models (10,11,15,16 It is interesting to note that in dog 75, despite a stable GFR in the diseased kidney, the sodium excretory pattern changed as the disease became chronic.…”

“…Sodium handling by the intact kidney in both models I and II was similar to the intact kidney in the dog model with a unilateral remnant or pyelonephritic kidney (11). Thus, it seems unlikely that a circulating antinatriuretic substance was responsible for decreased sodium excretion by the APGN kidney in group I.…”

“…However, the base-line FENa is actually significantly higher for the pyelonephritic kidney than control kidney even though the differences are small (11). The absolute difference in FEN.…”

“…Similarity of glomerulotubular balance in the diseased and intact kidney, however, is altered by extracellular fluid volume expansion. Both the chronically diseased glomerulonephritic and pyelonephritic kidney exhibit an exaggerated natriuresis per GFR compared to the contralateral intact kidney in response to an acute saline load (10,11). This suggests either that the change in internal milieu of the diseased kidney renders it more responsive to changes in oncotic or hydrostatic pressure in the peritubular capillaries, or that the chronically diseased kidney is more sensitive to a natriuretic substance released during volume expansion.…”

Micropuncture Studies of Sodium Tranport in the Remnant Kidney of the Dog THE EFFECT OF GRADED VOLUME EXPANSION

“…Although altered renal transport of sodium in chronic renal failure is well known and has been the subject of intensive investgation (1)(2)(3)(4)(5)(6)(7)(8)(9)(17)(18)(19), the manner by wnvhich this change in renal handling of sodium takes place at various sites of the nephron has not been elucidated. Micropuncture studies performed in the past using various experimental models have centered mostly on the transport changes in the proximal tubule (5)(6)(7)(8) and rarely in the distal segments (9).…”