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SUMMARY Cardiac output (CO) and renal blood How (RBF)were simultaneously evaluated by the microsphere method in water-drinking and chronic saline-drinking rats at 3 , 12, and 24 hours after induction of acute renal failure by glycerol injection. Three hours after glycerol injection CO and RBF decreased to 36% and 20% of the respective controls in water-drinking rats and to 41% and 24% of the controls in saline-drinking rats. Renal vascular resistance (RVR) increased significantly in both groups at this time. Isoncotic plasma expansion (3% of body weight) restored the RBF and RVR to normal in water-drinking rats 3 hours post-glycerol injection, although CO increased to only 70% of the control. Twelve hours after glycerol injection, CO and RBF returned to normal in saline-drinking rats, whereas they remained lower than controls in water-drinking rats. Twenty-four hours post-glycerol injection, when acute renal failure was evident as indicated by blood urea nitrogen (BUN) values of 116.9 and 63.8 ing/100 ml in water-and saline-drinking rats, respectively, CO and RBF returned to normal, except that the CO of waterdrinking rats was slightly higher than control. Thus, we conclude that decreased CO is an important determinant of the early decrease in renal perfusion in glycerol-induced acute renal failure. Furthermore, the observed earlier return of CO and RBF to normal in saline-drinking rats may be partly responsible for reducing the severity of acute renal failure.RECENT STUDIES have demonstrated that renal cortical ischemia is not responsible for maintenance of impaired glomerular filtration in experimental acute renal failure. "3 These findings are contrary to earlier reports that indicated a primary role for decreased renal perfusion in the severely decreased glomerular filtration rate (GFR) that occurs in acute renal failure. "7 However, a severe reduction of renal blood flow (RBF) during the initial hours of glycerol-induced acute renal failure has been consistently demonstrated 1 -4 -5 and such a reduction of RBF undoubtedly contributes to the early decrease of GFR seen in this model. The mechanisms for this reduction of RBF are not entirely clear, but it has been suggested that the renin-angiotensin axis and increased intrarenal vascular resistance 4 -5 ' 8> 9 may be involved. This study was designed to investigate the mechanism of decreased RBF in the early stage of glycerol-induced acute renal failure in water-drinking rats and chronic salinedrinking rats. MethodsExperiments were performed on male Sprague-Dawley rats weighing 180-300 g. Group I contained rats main- tained on Purina laboratory chow and tap water. In group II, rats were given 1 % NaCl instead of tap water to drink for 4-6 weeks prior to experimentation. Cardiac output (CO) and RBF were determined simultaneously by modified microsphere methods previously described. "13 Measurements were made in awake rats at 3,12, and 24 hours after intramuscular injection of 50% glycerol, 1 ml/100 g of body weight. All rats^were dehydrated for 15 hours prior ...

Ferric citrate shows promise as a means of lowering the serum phosphate concentration in haemodialysis patients. Further studies are needed to find the optimal dose.

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