THE EFFECTS OF SURGERY AND ACUTE REJECTION ON GLOMERULAR HEMODYNAMICSIN THE TRANSPLANTED RAT-KIDNEY

The effects of surgery and acute rejection on glomerular hemodynamics in the transplanted rat kidney are examined. Kidneys were transplanted from Munich-Wistar (MW) rats to syngeneic controls and MHC-incompatib le PVG strain recipients. We report on 4 groups of animals: (1) two-ki dney control MW rats; (2) unilaterally nephrectomized MW rats (UNX); ( 3) renal transplantation from MHC-identical MW littermates and removal of native kidneys (SYN); and (4) transplantation from MW donors to MH C-incompatible PVG rats and removal of native kidneys (ALLO). Glomerul ar filtration rate (GFR), single-nephron (SN)GFR, and glomerular capil lary pressure (P(GC)) in SYN kidneys were depressed as compared to tho se in UNX (GFR, 1.41+/-0.08 vs. 0.80+/-0.08 ml/min; SNGFR, 67.2+/-4.8 vs. 44.7+/-6.6 nl/min; and P(GC), 67+/-2 vs. 48+/-4 mmHg, UNX vs. SYN, respectively, P<0.05). GFR and SNGFR in ALLO kidneys, however, were d epressed even further (GFR, 0.40+/-0.05 ml/min; SNGFR, 13.8+/-1.8 nl/m in; P<0.05 for UNX vs. ALLO and SYN vs. ALLO). Afferent arteriolar res istance (R(A)) was increased greater than 4-fold (UNX, 1.01+/-0.15 10( 10) dyn-sec-cm-5; SYN, 1.37+/-0.36 10(10)dyn.sec.cm-5; ALLO, 4.76+/-0. 74 10(10)dyn.sec-cm-5 [P<0.05, UNX vs. ALLO and SYN vs. ALLO]). This l ed to a precipitous fall in initial capillary flow rate in ALLO rats. These studies reveal the presence of moderate reductions in SNGFR and P(GC) in the nonrejecting transplanted kidney, which may relate to as yet unidentified consequences of the transplant surgery. More signific antly, the principal mechanism leading to the reduced GFR characterist ic of acute allograft rejection is identified as severe preglomerular vasoconstriction.