Functional Compensatory Changes after Unilateral Nephrectomy in Rats

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Abstract
Cardiac output (CO), total peripheral resistance (TPR), renal blood flow (RBF), renal vascular resistance (RVR) and intrarenal blood flow distribution have been measured 48 h after unilateral (right) nephrectomy (UNX) and in sham-operated rats (SO). Glomerular filtration rate (GFR) and renal plasma flow (RPF) were determined using standard inulin and PAH clearances. Superficial single nephron GFR (SNGFR) was measured by free-flow micropuncture techniques. Extracellular fluid volume (ECV) and plasma volume (PV) were also determined. UNX rats showed increases of 17.4% in remnant kidney GFR and 34.5 % in RPF. Filtration fraction was decreased to 0.27 ± 0.01 (control value 0.31 ± 0.01; p < 0.0025). SNGFR was 45% higher in UNX rats and the ratio SNGFR/GFR increased by 28%. Cardiac output also increased (33.6 ± 1.0 for UNX rats; 28.0 ± 1.2 ml/min/100g BW for SO rats; p < 0.0025) accompanied by a corresponding fall (20%) in TPR. Left kidney RBF increased by 22%, whereas RVR decreased by 21%. Blood flow through individual glomer-uli increased in the outer and inner cortex and was unchanged in the midcortex. In conclusion, 48 h after unilateral nephrectomy, rats showed a hyperdynamic circulatory state with increased CO and decreased TPR; this could be involved in the acute adaptive functional and renal changes reported after uninephrectomy.