The Role Of Ketanserin, A Serotonin Receptor Blocker, In The Treatment Of Ischemic Acute Renal Failure
à Keskin, M Us, S Özkan, H Acar, C Top, O Öncul
Keywords
acute renal failure, fractional sodium excretion, ketanserin, renal function, serotonin
Citation
à Keskin, M Us, S Özkan, H Acar, C Top, O Öncul. The Role Of Ketanserin, A Serotonin Receptor Blocker, In The Treatment Of Ischemic Acute Renal Failure. The Internet Journal of Thoracic and Cardiovascular Surgery. 2002 Volume 6 Number 1.
Abstract
Prolonged and significant reduction of renal blood flow may cause acute renal failure (ARF). Serotonin is suggested to be responsible for vasoconstrictive effects.
Aims: To evaluate the effects of ketanserin, a serotonin receptor antagonist, on renal functions in rats with ischemic ARF that is induced by using vascular clamping technique. Twenty male wistar rats were studied, and the study consisted of four periods: Basal period: 60 min duration, drug: isotonic NaCl; Occlusion period: 60 min duration, no drug was administered; Infusion period: 60 min duration, Group 1 (control group) n=10, drug: isotonic NaCl, Group 2 (ketanserin group), n=10, ketanserin 0.05 mg/kg I.V bolus followed by 0.1 mg/kg/h I.V infusion; Recovery period: 300 min duration, drug: isotonic NaCl 2 ml/h I.V infusion. There were no significant differences between control and ketanserin groups in terms of creatinine clearance, urine output, fractional sodium excretion (FENa) and mean arterial pressures measured at basal period, occlusion period and 120th minute of recovery period (p>0.05). At the 300th minute of recovery period, there was a statistically significant increase in creatinine clearance, urine output and MAP values and there was a statistically significant decrease in FENa values (p<0.05) in the ketanserin group compared to the control group. We concluded that a 5-hydroxytriptamine-2 (5HT2) receptor blocker ketanserin has a favorable contribution on improvement of renal functions. This observation supports the idea that serotonin has a major role in post ischemic vasoconstriction and 5HT2 blockers counteracts this effect.
Introduction
Ischemic acute renal failure is the type of renal failure that develops when renal hypoperfusion of any reason could not be compensated by renal autoregulation and neurohumoral protection mechanisms (1). Decrease in the glomerular filtration rate following renal hypoperfusion and ischemia is due to two mechanisms: preglomerular vasoconstriction and tubular dysfunction. Multiple factors are responsible for intrarenal vasoconstriction and hypoperfusion of outer medulla (2,3). When experimental ischemic renal failure is induced in dogs and rats, it is demonstrated that serotonin synthesis was increased and consequently vasoconstriction of renal arcuate arteries, vasodilatation of small preglomerular vessels and a resultant decrease in glomerular blood flow occurred and it was suggested that serotonin has an important role in vasoconstrictive effect of ischemia (4). Serotonin is a biologically active amine. Besides serotoninergic nerve endings, serotonin is also synthesized at noradrenergic-dopaminergic nerve endings, enterocromaffin cells of gastrointestinal system, renal proximal tubule cells and thrombocytes (5,6,7). It was stated that serotonin increases renal blood flow in rat kidney (8) and it has a renal vasoconstrictive effect (9,10,11). Serotonin synthesis occurs in the proximal tubules of the normal rat kidney and vascular endothelial damage following ischemia results in an increase in post ischemic vasoconstriction by the serotonin released from thrombocytes (12,13). Dog, rabbit and rat kidneys have two types of serotonin receptors; 5-hydroxytriptamine-2 (5HT2) receptor leads to vasoconstriction and 5-hydroxytriptamine-1 (5HT1) receptor leads to vasodilatation (7,12,14,15). Favorable effect of ketanserin, a 5HT2 receptor blocker, to renal hemodynamics that is disturbed following ischemia is found in studies on rat kidney with induced ischemia (4,11,14,16). In the light of these studies, we aimed to investigate the effects of ketanserin, a 5HT2 receptor blocker, on rat kidney with induced ischemia, with vascular clamping method.
Materials and Methods
After Marmara University Ethics Committee approval, we used male wistar rats as subjects in this study (n=20, body weight=290 12g, mean age=3 months). Water intake was allowed before the study and they were given standard rat food. Interventions were done over a warmed floor so that the body temperature of the animals was kept between 37-38 C. The animals were given intraperitoneal urethane anesthesia (1200 mg/kg). The right jugular vein was cannulated by a poliethylen-10 (PE-10) catheter and isotonic NaCl solution was infused via this cannula at a rate of 2 ml/h, in order the replace fluid and electrolyte loss during surgical procedures. A PE-10 catheter was replaced at right internal carotid artery for blood sampling and intra-arterial pressure measurements. Another PE-10 catheter was placed into the bladder via a suprapubic incision for monitoring urine output and for obtaining urinary samples. Following preparation for surgical intervention, the experiment took place at the following four stages:
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Basal period: all subjects were given isotonic NaCl solution at a rate of 2 ml/h for 60 minutes.
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Occlusion period: following basal period, renal arteries were approached bilaterally via side incisions and clamped, a 60 minutes of transient occlusion was done.
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Infusion period: following removal of renal artery clamps, subjects were randomized into two groups (so that body weights were balanced between groups) each consisting of 10 rats. Each group received either the study drug or isotonic NaCl for 60 minutes. Groups and administered agents were as follows: Group 1: Control group; isotonic NaCl, 2 ml/h I.V infusion Group 2: ketanserin (Research Biochemical International, USA, S-006), 0.05 mg/kg I.V bolus followed by 0.1 mg/kg/h I.V infusion.
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Recovery period: during this period all cases received NaCl solution at a rate of 2 ml/h for 300 minutes.
Measurements were done at 120th and 300 th minutes of reperfusion were evaluated. At the end of each period and for each group, blood and urine samples were obtained to measure creatinine and sodium levels for creatinine clearance and FENa determination; in addition, urine output and mean arterial pressure were also measured. Serum and urinary creatinine levels were measured with auto an analyser (RA, 1000 Tecnicon Auto Analyzer, USA) by using Modified Jaffe (kinetic) method, and serum and urinary sodium levels were measured with auto analyser (RA, 1000 Tecnicon Auto Analyzer, USA) by using ion selective membrane. All data obtained during the study were presented as means and standard deviations. Significance of difference between mean values of groups were analysed with non-paired Mann-Whitney U test and p<0.005 was accepted as significant.
Results
Creatinine Clearance:
There was not any statistically significant difference between control and ketanserin groups in terms of mean creatinine clearance values, at basal, occlusion, infusion periods and at 120 th min. of reperfusion period (p>0.05). In measurements done at 300 th min. of reperfusion there was a statistically significant difference between control and ketanserin groups in terms of mean creatinine clearance (p<0.05) (Table 1).
Urinary Output:
There was not any statistically significant difference between control and ketanserin groups in terms of mean urinary output rate, at basal, occlusion, infusion periods and at 120th min. of reperfusion period (p>0.05). There was a statistically significant difference between two groups in terms of mean urinary output measured at the minute 300 of recovery period (p<0.05) (Table 1).
Figure 1
Fractional Sodium Excretion (FENa):
There was not any statistically significant difference between control and ketanserin groups in terms of mean FENa values, at basal, occlusion, infusion periods and at 120th min. of reperfusion period (p>0.05). At the 300 th minute of recovery period, mean FENa value was decreased in ketanserin group compared to control group and the difference between two groups was statistically significant (p<0.05) (Table 1).
Mean Arterial Pressure:
There was not any statistically significant difference between control and ketanserin groups in terms of mean arterial pressure measurements, at basal, occlusion, infusion periods and at 120th min. of reperfusion period (p>0.05). At the 300 th minute of recovery period, mean arterial pressure was increased in ketanserin group compared to control group and the difference between two groups was statistically significant (p<0.05) (Table 1).
Discussion
Severe renal ischemia in rats is induced by clamping renal arteries for 30-120 minutes (2,7,18). In this study, in order to induce renal ischemia in rats, both renal arteries were clamped simultaneously by microvascular clamps for 60 minutes. It was observed that both kidneys became pale and whitened, arterial pulse disappeared distal to the clamps and urinary output stopped. These were indicating that renal arteries were totally occluded and the findings were consistent with the studies of Tanner (18) and Arendshort in which renal artery occlusion was performed.
Creatinine Clearance:
Tanner and Schramm found that GFR decreased %10 below its basal value following 60 minutes of renal ischemia (18,20). GFR was 6.7 % of basal period value during infusion period in ketanserin group and it was 5.4 % of basal period value in control group (GFR was totally stopped during renal arterial occlusion). Our results were consistent with the findings of Tanner and Schramin (18,21). In control group, creatinine clearance was 9% of its basal value at 120th min of recovery period and it was 9.4% of its basal value at 300th minute of recovery period. In ketanserin group creatinine clearance was 8.9% of its basal value at 120th minute of recovery period. The difference was not statistically significant when compared with control group (p<0.05). However, in ketanserin group creatinine clearance at 300th minute of recovery period was 13% of its basal value and the difference was statistically significant when compared with control group (p<0.05). Marleen and colleagues first clamped aorta of male wistar rats and by this way they provided a 5 mmHg decrease in renal perfusion pressure, then they clamped right renal artery and induced a unilateral ischemia. This was followed by 0.05 ml/kg bolus and then 0.1 mg/kg/h infusions of ketanserin and they observed that ketanserin had a limited initial effect on ischemic rat kidney, but during the late recovery phase including 48 hours-7 days after reperfusion there were improvements in GFR up to 25-30% (16). Improvements of creatinine clearance in rats with ketanserin administration occurred earlier (in 300 minutes of recovery period) compared to the findings of Marleen and colleagues. Early positive effect on creatinine clearance may be due to the 2 ml/min infusion of NaCl for 300 minutes of recovery period and this infusion may have favorable contributions on glomerular blood flow.
Urine Output:
In the study of Marleen and colleagues, 11 of 15 rats that received ketanserin had anuria 48 hours after reperfusion and remaining 4 rats had a urine output which is 21% of observed in control group. At the 7 th day after reperfusion all rats had urine output and ketanserin group had 35% of control group's urine output (16). In our study, urine outputs of control group at infusion period, 120 th minute of recovery period and 300 th minute of recovery period reached to 67%, 74% and 80% of basal period, respectively. These values were 65%, 74% and 120% for ketanserin group, respectively. When urine outputs of ketanserin and control groups at the 120 th minute of recovery period were compared there was not any statistically significant difference (p>0.05), but urine outputs of two groups at 300 th minute of recovery period was statistically different (p<0.05). We observed that all rats had urine output from the beginning of reperfusion; this was different than Marlleen and colleagues' findings. We suggest that isotonic NaCl infusion administered at a rate of 2 ml/h for the recovery period may have a contribution to the increase in glomerular blood flow and the decrease in tubular obstruction and this may have led to our different findings.
Fractional Sodium Excretion (FENa):
Marleen and colleagues found that ketanserin did not effect urinary sodium excretion during acute phase but it decreased Na excretion during late phase. They observed that there was a significant decrease in FENa values compared to control group at the 48 th hour of recovery period and this returned to normal at the 7 th day (16). During the basal period of our study, mean FENa values of control and ketanserin groups were 0.14%, this shows that tubular functions were normal. FENa was decreased to zero when glomerular filtration was totally stopped during 60 minutes of renal arterial occlusion. FENa values increased significantly with the initiation of reperfusion; this shows that ischemic tubular damage had occurred and the balance between filtration and reabsorption had been impaired. There was not any statistically significant difference between ketanserin group and control group in terms of mean FENa values at the 120 th minute of recovery period (p>0.05). FENa mean value of ketanserin group measured at the 300 th minute of recovery period significantly decreased compared to mean value of control group and the difference between two groups was statistically significant (p<0.05). Our findings demonstrate that tubular sodium excretion in post ischemic rat kidney decreases earlier compared to the results of Marleen and colleagues (16).
Mean Arterial Pressure:
Matthys and colleagues investigated the relationship between renal blood flow and renal perfusion pressure in a rat model with induction of ischemic ARF. They found that renal blood flow decreased significantly (45%) when perfusion pressure was below 95 mmHg (17). Lamcire and colleagues used an ischemic model in which they induced ischemia by infusing the renal arteries of rats with 2 mcg of serotonin and 1 mcg of feniletrin and they administered high dose (0.75 mg/kg bolus, 2 mg/kg/h infusion) infusion of ketanserin in one group of rats and they administered low dose (0.05 mg/kg bolus, 0.1 mg/kg/h infusion) ketanserin in the other group. There were decreases in MAP values in high dose receiving group until 75 mmHg due to the presence of alpha-1 receptor blockade besides 5HT2 receptor blockade, but renal blood flow decreased only 25%. In low dose receiving group MAP values decreased to 104 mmHg from 118 mmHg, however renal blood flow increased 10.4% (from 5.17 ml/min to 5.71 ml/min) (4). Marleen and colleagues reported the MAP values at the 7 th day as 93-94 mmHg in rats that received ketanserin but they observed only a 4.5% decrease in renal blood flow (16). In our study we found that in ketanserin group there was a statistically significant increase in MAP compared to control group (p<0.05) and this effect was earlier (at the 300 th minute of reperfusion) than the results of Marleen study. This earlier positive effect may be due to the infusion of isotonic saline solution at a rate of 2 ml/h during 300 minutes of recovery period.
Conclusions
We conclude that ketanserin prevents vasoconstriction in the post ischemic rat kidney that is due to increased serotonin, therefore decreases ischemic damage and provides an improvement in renal functions. We suggest that concomitant isotonic NaCl infusion contributes favourably to the effect of ketanserin on ischemic kidneys functions. We suggest that ketanserin may provide clinical benefits in patients with ischemic ARF. Further experimental and clinical studies are needed.
Correspondence to
Dr. Melih Hulusi US GATA Haydarpaşa Egitim Hastanesi Kalp Damar Cerrahi Klinigi 81327- Kadiköy-Istanbul – Turkey Tel: +90 532 3157766 Fax: +90 216 3029929 e-mail: melihus@superonline.com
Acknowledgements
The experiments comply with the current laws of Turkey.