The functional state of the isolated rabbit kidney perfused with autologous blood

Abstract.

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* µl/g kw per min, urine flow from 5.58±1.13 to 4.91±0.75 µl/g kw per min, Na⁺ excretion from 1.07±0.19 to 0.63±0.12* µmol/g kw per min, K⁺ excretion from 0.46±0.03 to 0.28±0.05* µmol/g kw per min, P excretion from 2.5±0.2 to 2.0±0.5 µg/g kw per min, Ca excretion from 0.4±0.1 to 0.12±0.05* µg/g kw per min, creatinine excretion from 6.94±0.32 to 5.68±0.54 µg/g kw per min, glucose excretion from 18.2±3.2 to 1.6±0.5* µg/g kw per min, the free water clearance (CH₂O) from –6.57±0.85 to –5.10±1.31 µl/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 µmol/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.