Studies on the immediate change in renal function following unilateral nephrectomy
Numerous studies have been done on the morphological and functional change in the remaining kidney after an unilateral nephrectomy. Morphologically, a compensatory tubular proliferation (Roll-assn, 1949; Simpson, 1961) and hypertrophy (Rollason, 1947; Maulard and Cier, 1961) have been demonstrated in the remaining kidney after nephrectomy.
There are additional reports showing the following increased renal functions: glomerular filtration rate, renal Plasma flow (Smitk, 1941; Krohn et al., 1956), maximum concentrating and diluting capacity (Bradford, 1938; Ceburn et al., 1955), reabsorption and excretion of sodium (Hayslett,1968), oxygen consumption (Van Slyke, 1934 i Levy, 1935) and the activity of ATPase in the renal tubules (Kat2 and Epstein, 1957). Usually these functional and morphological changes in the remaining kidney had appeared by 2 weeks after an unilateral nephrectomy. Although, in recent years, a considerable number of studies concerning the hemodynamic changes and water electrolyte balance following unilateral nephrectomy have appeared; very little is known about the immediate renal change(s) after an unilateral
This experiment evaluated the early compensatory changes in renal function which were demonstrated immediately after an unilateral nephrectomy. Renal functions studied were GFR, RPF and urinary excretion of Na**+, K**+ etc. In addition, the tubular maximum transport capacity of glucose and PAH, and the changes in oxygen consumption were simultaneously determined.
Normal healthy adult dogs of either sexes weighing approximately 10-15 kg were used. The animals were subjected to different experimental conditions before nephrectomy depending upon the nature of the experiment i.e. dehydrated, or ECF was
expanded by infusing one of 0.9% NaCl, isotonic mannitol or 2% NaCl solutions.
After infusions of appropriate amounts of inulin, PAH, three consecutive control samples of plasma and urine at 10 minutes intervals were obtained before unilateral nephrectomy. Samples of plasma and urine were obtained at 20 minutes intervals for 5hours after nephrectomy. The concentration of inulin, PAH, osmolarity, Na**+, K**+ and urea of the samples were determined.
Results are summarized briefly as fellows.
1) When the ECF was expanded by the infusion of mannitol and then the d7g was unilaterally nephrectomized, decreases after nephrectomy in both GFR and RPF were demonstrated. However, in other experimental groups, the renal plasma flow gradually declined to level of 20∼40% of nor-mal while there was no change in the GFR.
2) In the dehydrated state, urinary excretion of sodium was slightly increased in the unilaterally nephrectomized animals as compared to the controls. On the contrary, when isotonic or hypertonic(2%) sodium chloride solution was infused pre·operatively into the animals and then they were unilaterally nephhrectomized, the excretion of sodium was markedly increased. This increase in sodium excretion was observed from 3 hours after the unilateral nephrectomy was performed.
3) An increase in Na**+ excretion after nephreotomy was demonstrated only in the groups whose ECF was expanded by infusions of NaCl solution (0.9? and 27) but was not demonstrated in the groups whose ECP had been expanded by isotonic mannitol.
4) The capacity for glucose reabsorption in the remaining kidney was not altered as compared to that seen in control animals. However, the tubular secretion of PAH was significantly reduced.
5) Essentially oxygen consumption was not changed by the unilateral nephrectomy. On the basis of above findings, it is postulated that a significant increase in sodium excretion after unilateral nephrectomy when the ECF had been expanded by an infusion of sodium chloride was the result of inhibition of sodium reabsorption in the distal nephrons and the proximal tubules.
The compensatory mechanisms in the remaining kidney appeared as early as 3 hrs. after unilateral nephrectomy. However, the mechanism for the reduced PAH secretion is unknown and further experiments will be required to find the reason for the decrease.