This report describes the technique and procedure for perfusing an isolated rabbit kidney with 25 ml heparinized autologous blood in a closed circuit including a pump and an oxygenator. The duration of the operative ischaemia was 5-8 min; the perfusion lasted 2.5 hours. An additional infusion was made to compensate for urinary losses. Renal blood flow increased progressively from 2.01+/-0.1 to 2.65+/-0.22* ml/g kidney weight (kw) per min (*P<0.05). Between the first (P1) and the last (P4) urine collection period the glomerular filtration rate (GFR) fell from 288+/-25 to 217+/-38* microl/g kw per min, urine flow from 5.58+/-1.13 to 4.91+/-0.75 microl/g kw per min, Na+ excretion from 1.07+/-0.19 to 0.63+/-0.12* micromol/g kw per min, K+ excretion from 0.46+/-0.03 to 0.28+/-0.05* micromol/g kw per min, P excretion from 2.5+/-0.2 to 2.0+/-0.5 microg/g kw per min, Ca excretion from 0.4+/-0.1 to 0.12+/-0.05* microg/g kw per min, creatinine excretion from 6.94+/-0.32 to 5.68+/-0.54 microg/g kw per min, glucose excretion from 18.2+/-3.2 to 1.6+/-0.5* microg/g kw per min, the free water clearance (CH2O) from -6.57+/-0.85 to -5.10+/-1.31 microl/g kw per min and urine osmolality from 600+/-52 to 590+/-105 mOsm/kg, urea excretion from 0.75+/-0.16 to 0.95+/-0.13 micromol/g kw per min. Excretion of glucose, P or Ca was observed only above a given plasma threshold value, and no transport maximum was found for glucose or P. Ca reabsorption paralleled the Na reabsorption. The proximal tubule pressure, measured within the 1st h of perfusion, was 12.5+/-1.1 mm Hg. Histological examination at the end of the perfusion showed dilatation of the tubules as in the non-perfused kidneys, and the presence of numerous bacteria. Hypertonic urine (380-1110 mOsm/kg) was observed in the presence of vasopressin, in the latter's absence the urine was hypotonic urine (206-278 mOsm/kg). There was no correlation between renal plasma flow and the GFR. CH2O increased with increasing filtered Na+ load. In conclusion, the blood-perfused, isolated rabbit kidney has a fairly constant functional capacity for approximately 2 h.
Background/Aims: Hypoxia may play a role in the development of renal failure in donated kidneys. In the present study, the effects of hypoxia on isolated blood-perfused rabbit kidneys were investigated and the effects of mannitol were explored, giving special attention to intratubular pressure. Methods: Kidneys were perfused with their autologous blood during four 30-min periods (P1–P4). P1 was considered baseline function. In P2, hypoxia was induced either alone or with an infusion of mannitol (15 mg/min) during P2–P4. Reoxygenation was applied after P2. Proximal intratubular pressure was measured in all conditions. Results: During hypoxia, renal blood flow doubled and restored immediately in P3. Urine flow stopped in P2, except in the series with mannitol, but gradually resumed in P3 and P4. Likewise, creatinine clearance recovered slightly (<25%) in P4, except for the series with mannitol, where it still could be measured in P2 and reached a value >50% of P1. Proximal intratubular pressure (mean ± SD) increased from 12 ± 5 in P1 to 24 ± 11 mm Hg during hypoxia and returned to 10 ± 6 mm Hg in P3. This increase was not observed with mannitol. Conclusion: Cellular swelling might be responsible for the suppressed filtration during hypoxia and can be prevented by mannitol.
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