Lack of effect of antioxidant therapy during renal ischemia and reperfusion in dogs

Is midazolam effective as an antioxidant in preventing reperfusion injury in rat kidney?

This experimental study was designed to investigate whether midazolam has antioxidant effects in reperfused rat kidneys following ischemia. Twenty Wistar Albino rats were included in the study. Rats were anesthetized with the mixture of ketamine 90 mg/kg and xylazine 10 mg/kg administered intraperitoneally. Following anesthesia, the rats were divided into two groups. The first group was considered as the control group, whereas the second group received additional midazolam 3.5 mg/kg intraperitoneally. The left kidney was approached via a transabdominal incision and the left renal artery was dissected. Left renal ischemia was created by clamping the left renal artery for 45 minutes. Following the ischemia period, the kidney was reperfused for one hour. Both kidneys were then removed. Half of the left kidneys were immediately immersed in liquid nitrogen for transportation and then frozen at -70 C until measurements of tissue malondialdehyde (MDA) and glutathione (GSH) levels. The remaining halves of the left kidneys and right kidneys were fixed in 10% formalin. The changes which developed during the ischemia-reperfusion period in the left kidney were investigated by histopathological examination and compared with those of the normal contralateral kidney. When compared with the control group, tissue MDA and GSH levels were similar in the midazolam group (p > 0.05). Tubular damage with tubulitis and focal interstitial inflammatory infiltration were observed in histopathological examinations of reperfused left kidneys of the control group. There was PMNL infiltration only in perirenal fat tissue of the midazolam group. Right kidneys were histopathologically normal in both groups. We concluded that within this dosage midazolam does not have any antioxidant effect in reperfused rat kidneys following ischemia.

Renal handling of drugs and amino acids after impairment of kidney or liver function--influences of maturity and protective treatment

Renal tubular cells are involved both in secretion and in reabsorption processes within the kidney. Normally, most xenobiotics are secreted into the urine at the basolateral membrane of the tubular cell, whereas amino acids are reabsorbed quantitatively at the luminal side. Under different pathological or experimental circumstances, these transport steps may be changed, e.g., they may be reduced by renal impairment (reduction of kidney mass, renal ischemia, administration of nephrotoxins) or they may be enhanced after stimulation of transport carriers. Furthermore, a distinct interrelationship exists between excretory functions of the kidney and the liver. That means liver injury can influence renal transport systems also (hepato-renal syndrome). In this review, the following aspects were included: based upon general information concerning different transport pathways for xenobiotics and amino acids within kidney cells and upon a brief characterization of methods for testing impairment of kidney function, the maturation of renal transport and its stimulation are described. Similarities and differences between the postnatal development of kidney function and the increase of renal transport capacity after suitable stimulatory treatment by, for example, various hormones or xenobiotics are reviewed. Especially, renal transport in acute renal failure is described for individuals of different ages. Depending upon the maturity of kidney function, age differences in susceptibility to kidney injury occur: if energy-requiring processes are involved in the transport of the respective substance, then adults, in general, are more susceptible to renal failure than young individuals, because in immature organisms, anaerobic energy production predominates within the kidney. On the other hand, adult animals can better compensate for the loss of renal tissue (partial nephrectomy). With respect to stimulation of renal transport capacity after repeated pretreatment with suitable substances, age differences also exist: most stimulatory schedules are more effective in young, developing individuals than in mature animals. Therefore, the consequences of the stimulation of renal transport can be different in animals of different ages and are discussed in detail. Furthermore, the extent of stimulation is different for the transporters located at the basolateral and at the luminal membranes: obviously the tubular secretion at the contraluminal membrane can be stimulated more effectively than reabsorption processes at the luminal side.

Improvement of therapeutic effect of human recombinant superoxide dismutase on ischemic acute renal failure in the rat via cationization and conjugation with polyethylene glycol

Therapeutic effect of superoxide dismutase (SOD) and three derivatives: a conjugate with polyethylene glycol (SOD-PEG2), a cationized derivative (cSOD), and a mannosylated derivative (Man-SOD), on acute renal failure induced by ischemia/reperfusion was studied in rats. SOD and derivatives were administered intravenously to the rat after nephrectomy of the right kidney and before and after 60 min occlusion of the left renal artery. At 48 hr after reperfusion, the renal function was evaluated by determining the urinary excretion rate of 14C-inulin injected intravenously. No therapeutic effect on the impaired renal function was shown in the case of low dose SOD (2600 unit/kg) treatment. In contrast, administration of cSOD which was shown to be taken up by the isolated perfused kidney from its capillary side and SOD-PEG2 which maintained high plasma concentration exhibited significant therapeutic effect, as did SOD at ten-fold higher dose (26,000 unit/kg). On the other hand, renal damage was promoted by Man-SOD. Thus, the present study demonstrated that chemical modification may improve the therapeutic effect of SOD on the ischemic acute renal failure and increased SOD concentration in the renal vascular space is an important factor for the improved effect.