Tohoku J. exp. Med., 1966, 89, 69-76 Effect of Bradykinin and Eledoisin on Renal Function in the Dog Takashi Furuyama,. Chikara Suzuki, Hiroshi Saito, Yozo Onozawa , Ryuji Shioji, Shozo Rikimaru, Keishi Abe and Kaoru Yoshinaga Department of Internal Medicine (Prof. T. Torikai), Tohoku University School of Medicine, Sendai Bradykinin (0.05, 0.1 and 0.2 ƒÊg/kg/min) and eledoisin (0.5, 1.0, 5.0 and 10.0ng/kg/min) were infused directly into the left renal artery of anesthetized dogs to demonstrate the effects of these peptides on renal function. Urinary volume, endogenous creatinine clearance (GFR), PAR clearance (RPF) and excretion of electrolytes were increased by infusion of these two peptides, but no constant change was observed in UK/U ,Va ratio. These data demonstrate that the increase in urinary output and electrolyte excretion is caused by the augmentation of tubular load of solutes which resulted from the increase of RPF and GFR. Tachy phylaxis was observed in dogs which received repeated infusions of bradykinin but this phenomenon was less distinct in the case of eledoisin. Bradykinin is a nonapeptide formed by the action of kinin-forming enzymes upon alpha-2-globulin fraction of the plasma and it plays an important role in the local control of blood flow to certain tissues. On the other hand, eledoisin isolated from the salivary gland of Eledone, is endecapeptide having powerful kinin-like activity2. Bradykinin and eledoisin administered intravenously produce reduction in systemic blood pressure because of vasodilator action of the peptides.2,3 Since the change in systemic blood pressure affects renal function in experiments with intravenous infusion of the peptides, it is difficult to reveal their direct action on the kidney. The experiments to be reported here were designed to determine changes in renal functions in response to bradykinin and eledoisin directly administered to the kidney. METHODS Five dogs were used for bradykinin infusion and 4 dogs for eledoisin. Mongrel dogs of both sexes, weighing from 9 to 15 kg were anesthetized with 30 mg/kg of sodium pentobarbital. Both ureters were exposed through a midline incision and catheterized with polyethylene tubings which were pushed up into the renal pelvis and tied securely in place. A polyethylene catheter was inserted from Received for publication, February 25, 1966. 69 10 T. Furuyama et at. the right femoral artery to the left renal artery and the tip of the catheter was placed so as to stay for approximately 1.5 cm in the left main renal artery. Another catheter was placed into the left femoral artery and it was connected to n electronic manometer to record the blood pressure. These procedures were performed at least 30 minutes before beginning experimental observations. The priming doses of p-aminohippurate (PAH) was given intravenously, and then PAH dissolved in isotonic glucose solution was infused at a constant rate. Synthetic bradykinin or eledoisin was dissolved in 5 per cent glucose solution and infused at a rate of 0.5 ml/min through the polyethylene catheter placed into the left renal artery. In the preliminary observations, isotonic glucose infused at a rate of 0.5 ml/min into the renal artery had no effect on the renal function. The rate of infusion of bradykinin was 0.05, 0.1 and 0.2 ,ƒÊg/kg/min and that of eledoisin 0.5, 1.0, 5.0 and 10.0 ng/kg/min, respectively. Each clearance period was 10 to 20 minutes, and the intervals of peptide infusion were approximately 10 minutes. PAH and creatinine concentrations were estimated using a Beckman DB spectrophotometer (Brod and Sirota, and Smith),9 plasma and urinary concentrations of sodium and potassium were analyzed by a flame-photometer and systemic blood pressure was continuously recorded using an electronic manometer (Nihon Koden Co. Ltd.). Fig. 1. Changes of systemic blood pressure produced by infusion of bradykinin (a) and eledoisin (b) into the left renal artery. Bradykinin and Renal Function 71 Fig. 2. Effects of the direct infusion of bradykinin into the renal artery on renal function. --•œ----•œ-- shows changes of renal function when bradykinin was infused in the order of 0.05, 0.1 and 0.2 ƒÊg/kg/min. RESULTS 1) Bradykinin infusion into the renal artery The infusion of bradykinin into the left renal artery at the rates of 0.05 to 0.2,ƒÊg/kg/min produced no change in the systemic blood pressure (Fig. 1 a) and in the functions of right kidney including urine volume, endogenous creatinine clearance (GFR), PAH clearance (RPF) and urinary excretion of sodium and potassium. In each experiment, urine volume increased on the infused side, and the augmented urinary volume fell immediately to the control level, when the infusion of bradykinin was discontinued. Moreover, RPF and GFR were 72 T I??Furuyama et al. Fig. 3. Changes of renal function when bradykinin was infused into the left renal artery in the order of 0.05, 0.1 and 0.2ƒÊg/kg/min. -•ü-•ü- shows renal function of the kidney on the infused side. --•œ----•œ-- shows that of the kidney on the control side . increased by infusion of bradykinin in all dogs. Sodium and potassium excretions were also increased, but the augmentation in potassium excretion was less than that in sodium excretion. With the exception of one dog, the extrac tion fraction of sodium (excreted Na/filtered Na) was increased in all dogs, but no constant change was observed in urinary K/Na ratio (Fig. 2). When bradykinin was infused in the order of 0.05, 0.1 and 0.2,ƒÊg/kg/min, the increment of the urinary volume at 0.2 ƒÊg/kg/min of bradykinin was less than that of 0.1,ƒÊg/kg/min (Fig. 3). In contrast, when bradykinin infusion was started from 0.2,ƒÊg/kg/min, then followed by 0.05 and 0.1,ƒÊg/kg/min, urinary volume was maximum at 0.2,ƒÊg/kg/min infusion (Fig. 4). Bradykinin and Renal Function 73 Fig. 4. Changes of renal function when bradykinin was infused into the left renal artery in the order of 0.2, 0.05 and 0.1 ƒÊg/kg/min. -•ü-•ü- shows renal function of the kidney on the infused side. --•œ----•œ-- shows that of the kidney on the control side. This phenomenon was also observed in RPF, GFR and electrolytes excretion, indicating a tachyphylactic action of bradykinin on renal function. 2) Eledoisin infusion into the renal artery The direct renal infusion of eledoisin at a rate of less than 5.0 ng/kg/min produced no change in the systemic blood pressure. But the systemic blood pressure was decreased by about 30 mmHg by 10.0 ng/kg/min of eledoisin (Fig. 1 b). Furthermore, when a dose of 20.0 jig/kg/min of eledoisin was infused, the blood pressure fell below 60 mmHg and an immediate cessation of urinary output was observed. 74 T. Furuyama et al. Fig. 5. Effects of the direct infusion of eledoisin into the renal artery on renal function. The effects of eledoisin on renal function were essentially similar to those demonstratedwith bradykinin infusion. Namely, the increaseof urinary volume, GFR, RPF, and electrolyte excretion was also observed during eledoisin infus ion, but no constant changewas obtained in extraction fraction of sodium and urinary K/Na ratio (Fig. 5). Since the minimal effective dose of eledoisin was 0.5 ng/kg/min, this peptide was more effective than bradykinin on the renal function. Tachyphylaxis was observed in one of three dogs, but we could not reveal this phenomenon in the other two dogs. COMMENT The present experiments demonstrated that urine flow, RPF, GFR and electrolyte excretion were increased by direct renal infusion of bradykinin. Bradykinin and Renal Function 75 Similar observations were reported by Heidenreich and his associates,4 Webster and Gilmore,5 and Barraclough and Mills.' Heidenreich concluded that the increase of urine volume and electrolyte excretion resulted from direct action of this peptide on the tubular cells. In our experiments, the increase of RPF and GFR was observed by direct renal infusion of bradykinin. The urinary volume and the sodium excretion were increased in pallalel with increase of GFR and RPF. Furthermore, extraction fraction of sodium was increased in four of five dogs by bradykinin infusion, but no constant change was observed in urinary K/Na ratio. These results indicate that the increase of glomerular filtration which results from vasodilator effect of bradykinin plays an important role in the mechanism of the augmentation of urinary volume and electrolyte excretion. Moreover, since the increase in medullary blood flow rate results in a decrease of the renal concentrating ability,7 it is possible that augmented medullary blood flow due to the vasodilator action of bradykinin may play a role in the increase of urinary volume. It is not absolutely necessary to assume a direct tubular effect of bradykinin to account for its influence on the renal function. If bradykinin was infused repeatedly, the renal response to the peptide, especially urinary output, was reduced in all cases. Namely, the effect of 0.1,ƒÊg/ kg/min of bradykinin was more powerful than that of 0.2 ,ƒÊg/kg/min when the peptide was administered in order of 0.05, 0.1 and 0.2 ,ƒÊg/kg/min. On the other hand, in case in which the peptide was administered in order of 0.2, 0.05 and 0.1 ,ƒÊg/kg/min, the most effective dose of bradykinin on renal function was 0.2 ,ƒÊg/kg/ min, and the effect of 0.1 ƒÊg/kg/min was practically equivalent to that of 0.05 ,ƒÊg/kg/min.