RESPONSES TO HEMORRHAGIC ARTERIAL-PRESSURE REDUCTION IN DIFFERENT ISCHEMIC RENAL-FAILURE MODELS

Renal blood flow (RBF) autoregulation has been found to be impaired in both norepinephrine (NE) and renal artery clamp (RAC) rat ischemic ac ute renal failure models. However, the decline in RBF at the normal lo wer limit of autoregulation is greater in NE-ARF. The present study wa s designed to determine if this difference in autoregulatory profiles has potential functional and morphologic significance. After demonstra ting a fall in RBF to renal perfusion pressure reduction to 90 mm Hg t hat was twofold more in one week NE- than RAC-ARF (p < 0.001), separat e rats of both ischemic ARF types with nearly identical levels of azot emia and glomerular filtration rate reduction and sham-ARF rats were s ubjected to four-hour controlled reduction in mean arterial pressure t o 90 by transient phlebotomy at one week. On day 9, two days after mea n arterial pressure reduction, blood urea nitrogen (BUN), serum creati nine (S-Cr) and creatinine clearance (C-Cr) showed continued improveme nt in RAC-ARF, but there were significant increases in BUN (46 +/- 22 to 72 +/- 10 mg/dl) and S-Cr (1.2 +/- 0.2 to 1.5 +/- 0.2 mg/dl) and a decline in C-Cr (0.434 +/- 0.127 to 0.334 +/- 0.079 ml/min) in the NE- ARF group (all P < 0.02). The mean sum of scores of morphologic indice s of ARF was higher in NE- than RAC-ARF kidneys of rats sacrificed on day 9 but interstitial edema was the only individual index that was wo rse in NE-ARF. By day 14, function parameters had improved in both ARF groups, but BUN remained significantly higher in NE-ARF than the RAC- ARF group (P < 0.01). It is concluded that there is a distinct differe nce in susceptibility to recurrent injury and azotemia in NE- and RAC- ARF which is likely related to differences in maintenance phase renova scular reactivity in these two ischemic ARF models.