Urinary Concentration and Dilution after Unilateral Nephrectomy in the Rat

Abstract

1. The effects of unilateral nephrectomy on urinary concentration and dilution were studied in Sprague-Dawley rats. To exclude incomplete suppression of antidiuretic hormone, free water formation was also sutdied in rats with congenital diabetes insipidus (Brattleboro strain). 2. Urinary solute-free water formation was similar in Sprague-Dawley and Brattleboro rats. Uninephrectomized animals excreted a water load promptly and diluted their urine to the same degree as control rats. Maximal values for Cwater and TCwater per kidney were higher after nephrectomy, but were similar to those of control rats at comparable rates of fluid delivery to the distal nephron. Renal tissue osmolaity was similar in uninephrectomized and sham-operated animals, indicating that nonantidiuretic hormone-dependent backflux of filtrate was the same in the two groups. The only defect observed in uninephrectomized animals was a small reduction in maximal urine osmolaity. 3. These results demonstrate that free water formation and reabsorption are unaffected by unilateral nephrectomy and suggest that, in the remaining kidney, filtrate reabsorption along the entire nephron increases in proportion to the increment in glomerular filtration.

Early enhancement of fluid transport in rabbit proximal straight tubules after loss of contralateral renal excretory function.

“…Since animal-to-animal variations in net transtubular fluid transport in PST contribute to the variability reabsorption rate; MP, methylprednisolone; Pa, mean arterial blood pressure; PAH, p-aminohippurate; PCT [10][11][12][13][14][15][16][17][18][19][20] mmHg during the first 30-60 min after blood pressure recording was begun and then became stable. Rabbits in which Pa fell by 30 mmHg or more, or in which mean Pa was <70 mmHg, were discarded.…”

“…Although the chronic adjustments in nephron size (2,3), glomerular filtration rate (GFR)' (3)(4)(5)(6)(7), I Abbreviations used in this paper: AL, apparent tubule luminal surface area; As, apparent tubule serosal surface area; BW, body weight; C, control tubule; CIN, inulin clearance; CPAH, PAH clearance; EXP, experimental tubule; FENa, fractional sodium excretion; GFR, glomerular filtration rate; ID, tubule inner diameter; Jv, net fluid volume and tubule sodium and water reabsorption (7)(8)(9)(10)(11)(12) that result have been well studied, less attention has been paid to the early alterations in renal function and morphology that follow loss of functional renal tissue. Recent studies indicate that within several hours after unilateral nephrectomy (UNX) in volume-replete animals, the remaining kidney exhibits a significant rise in GFR and filtered load of sodium (13,14).…”