Pathogenesis of renal failure due to aminoglycosides and contrast media used in roentgenography

Contrast Media-Induced Renal Morphologic Lesions in Diabetic Rats

Diabetes mellitus was induced in rats with streptozotocin and after 3 months the animals (n = 48) received an i.v. injection of 1 or 3 g I/kg in the form of high-osmolar diatrizoate, low-osmolar iopromide or iohexol, or of 0.6 g I/kg of high-osmolar Gd-DTPA. The controls were given an i.v. injection of physiologic saline. After 2 hours the kidneys were fixed by perfusion and the renal morphologic changes were semiquantitatively analyzed by two independent observers unaware of the agent administered. The contrast media (CM) induced pronounced cytoplasmic vacuolization in the proximal convoluted tubular cells. Such a lysosomal alteration may indicate CM uptake into the cell, and the ultrastructural evaluation revealed intracellular injuries related to the process. The alterations were most marked following administration of iohexol, but diatrizoate also induced a statistically highly significant vacuolization (p < 0.001). The lysosomal alterations following iopromide administration were not as striking, and Gd-DTPA induced only minor changes.

Acute kidney injury and chronic kidney disease after cardiac surgery

Kidney dysfunction is common after cardiac surgery and predicts mortality risk and poorer long-term outcome, particularly when acute injury superimposes upon chronic kidney disease. Numerous insults contribute to perioperative renal impairment including major surgical trespass, procedure-specific interventions (eg, deep hypothermic circulatory arrest), and postoperative complications. Regardless of cause, evidence supports a role for renal impairment and accumulation of "uremic toxins" as direct contributors to adverse outcome. No one has yet characterized a loss of renal function small enough to be insignificant. Despite considerable research focus, progress in development of interventions aimed at perioperative renoprotection has been disappointing. However, practice modifications can influence the likelihood of acute kidney injury, and several recent advances provide hope for the future. We review pathophysiologic understanding of this disorder; evaluate the confusing relationship (causal v epiphenomena) among acute kidney injury, chronic kidney disease, and adverse outcome after cardiac surgery; and provide an evidence-based assessment of the conduct of cardiac surgery and renoprotection strategies.

Drug-induced renal function impairment: a population-based survey

PURPOSE

The knowledge that drugs can affect renal function is mainly based on experimental studies or case reports. Thus, it has only been investigated in selected populations. Here we describe drug groups associated with altered renal function in the general population.

METHODS

To study this, we used baseline data of 8592 subjects of a population-based cohort. Hyper- and hypofiltration were defined as a filtration above or below the 90% confidence interval of age-and-sex-corrected creatinine clearance. Drug use was measured in the year preceding the kidney function measurement.

RESULTS

The prevalence of hyperfiltration (4.6% in the general population) was higher among subjects using anti-diabetics (11.7%), dermatological corticosteroids (5.9%) and sex hormones (5.8%), but lower in subjects using anti-thrombotics (2.4%) and diuretics (2.1%). Hypofiltration (4.3% in the general population) was seen more often in users of beta blockers (6.2%), ACE inhibitors (7.1%), statins (7.2%), anti-thrombitics (6.8%), trimethoprim (7.9%), vaccines (9.4%), NSAIDs (5.2%), anti-ulcer agents (6.3%), laxatives (7.7%) and eyedrops (6.7%).

CONCLUSIONS

Several drug groups found in this overview were to be expected, since patients with kidney disease often use them (e.g. cardiovascular drugs). Several other drug groups were somewhat unexpected and deserve further attention.

The renal effect of low-dose dopamine in high-risk patients undergoing coronary angiography

OBJECTIVES

The purpose of the study was to examine the potential renal protective effect of low-dose dopamine in high-risk patients undergoing coronary angiography.

BACKGROUND

Contrast nephropathy is prevalent in patients with chronic renal failure (CRF) and/or diabetes mellitus (DM). Decreased renal blood flow due to vasoconstriction was suggested as a contributory mechanism. Low-dose dopamine has a dilatory effect on the renal vasculature.

METHODS

Sixty-six patients with mild or moderate CRF and/or DM undergoing coronary angiography were prospectively double-blindedly randomized, to either 120 ml/day of 0.9% saline plus dopamine 2 microg/kg/min (Dopamine group) or saline alone (Control group) for 48 h.

RESULTS

Thirty-three Dopamine-treated (30 diabetics and 6 with CRF) and 33 Control (28 diabetics and 5 with CRF) patients were compared. Plasma creatinine (Cr) level increased in the Control group from 100.6+/-5.2 before to 112.3+/-8.0 micromol/liter within five days after angiography (p = 0.003), and in the Dopamine group from 100.3+/-5.4 before to 117.5+/-8.8 micromol/liter after angiography (p = 0.0001), respectively. There was no significant difference in the change of Cr level (deltaCr) between the two groups. However, in a subgroup of patients with peripheral vascular disease (PVD), deltaCr was -2.4+/-2.3 in the Control group and 30.0+/-12.0 micromol/liter in the Dopamine group (p = 0.01). No significant difference occurred in deltaCr between Control and Dopamine in subgroups of patients with preangiographic CRF or DM.

CONCLUSIONS

Contrast material caused a small but significant increase in Cr blood level in high-risk patients. There is no advantage of dopamine over adequate hydration in patients with mild to moderate renal failure or DM undergoing coronary angiography. Dopamine should be avoided in patients with PVD exposed to contrast medium.

Renal cortical retention on delayed CT after angiography and contrast associated nephropathy

The aim of this study was to examine the relationship between renal cortical retention (RCR) of contrast media observed on delayed CT (median delay: 20 h) and contrast associated nephropathy (CAN). We investigated the incidence of both phenomena in 270 patients. CAN was defined as an increase in the creatinine level > 0.5 mg dl-1 (44 mumol l-1) and > 25% on day 1, 3 or 7, while RCR was recognized when CT values for the renal cortex showed either mild RCR (CT value > 50) or severe RCR (CT value > 100). RCR was demonstrated in 127 patients (47%), mild in 78 (29%) and severe in 49 (18%), on delayed CT after angiography. CAN was found in eight patients (3%). Patients with severe RCR showed a higher CAN rate (8%) than other patients (mild RCR: 4%, RCR (-): 1%) (p = 0.02). The type of contrast medium was independently associated with the incidence of RCR (p = 0.0001). Although severe RCR was associated with a higher frequency of CAN than the milder forms of RCR, RCR as such was not always associated with CAN.

Focal residual contrast media in the kidney 24 hours after angiography

PURPOSE

To examine the relationship between focal renal cortical retention (FRCR) and contrast-associated nephropathy (CAN).

MATERIAL AND METHODS

We investigated the incidence of both phenomena in 105 patients. CAN was defined as an increase in the creatinine level > 0.3 mg/dl and > 20% on days 1, 3, or 7. We compared predisposing factors for FRCR and CAN. Serum creatinine and blood urea nitrogen (BUN) for renal function were determined on the morning of the day of the angiography. The BUN/creatinine ratio was used as an indicator of the degree of hydration.

RESULTS

FRCR was demonstrated in 17 patients (16%) by delayed CT 24 h after angiography, and CAN was found in 16 patients (15%). No significant relationship between CAN and FRCR was found. We found a correlation between high total volumes of contrast and FRCR. Advanced age, high blood urea nitrogen, high creatinine, and dehydration were risk factors for CAN.

CONCLUSION

Delayed CT showed a higher incidence of injury to the renal parenchyma than previously detected by conventional radiography.

Renal scintigraphy in initial evaluation of renal colic

To determine the role of renal scintigraphy (RS) in patients with suspected acute urinary tract obstruction, a prospective study was performed comparing RS with emergency intravenous excretory urography (IVU) in 36 examinations. Thirty patients were diagnosed as having renal colic: 28 had dilation of the urinary tracts with (89%) or without (11%) visualized stone; 2 patients with stones did not have stasis at the IVU. An abnormal RS was found in 28 patients with abnormal IVU, while it was normal in the 2 nonobstructed patients (sensitivity = 93%). The radiopaque stones in these 2 patients were seen on plain x-ray film of the abdomen. The results of this study support the use of RS combined with a plain film of the abdomen in the initial evaluation of renal colic.

Radiocontrast-induced nephropathy in humans: role of renal vasoconstriction

Radiocontrast-induced nephropathy (RCIN) is a common cause of acute renal failure in hospitalized patients. Renal vasoconstriction figures prominently in the proposed pathogenesis of RCIN based on animal experiments. Prior human studies examining renal hemodynamic changes after contrast medium (CM) injection are inconclusive. No previous study of animals or humans has established a relationship between CM-associated renal hemodynamic changes and the subsequent development of RCIN. In the present study, we examined the renal hemodynamic effects of CM in patients at high risk of RCIN. In addition, we related those effects to the subsequent development of RCIN. Using renal vein thermodilution catheters, we measured renal blood flow (RBF) in 12 patients with chronic renal failure [serum creatinine (SCr) greater than or equal to 159 mumol/liter] during ionic CM injection for cardiac catheterization. We made measurements at the start of the procedure (t = 0), before the ventriculogram (t = 5), after the ventriculogram (t = 15), and after the coronary angiogram (t = 65). We measured SCr at t = 0 and again 24 and 48 hours later. Mean RBF for the group tended to increase after the ventriculogram, and increased significantly by t = 65 (P less than 0.005 vs. t = 0). When examined by individual patient, RBF fell below baseline in three patients (30%) at t = 15, but rose above baseline again by t = 65. Only one patient (8.3%) had a fall in RBF below baseline at t = 65. RCIN (defined as an increase in SCr greater than or equal to 25% above baseline) developed in six patients (50%) within 48 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of recombinant human erythropoietin on new anaemic model rats induced by gentamicin

The effects of recombinant human erythropoietin (r-HuEPO) on haematological parameters were studied in rats in which uraemia and anaemia had been induced by gentamicin, an aminoglycoside antibiotic and a nephrotoxic agent. After the occurrence of slight polycythaemia, the red blood cell count, haematocrit and haemoglobin concentration decreased by 20-30% compared with those of the control (saline-injected) rats. At the end of gentamicin treatment, the endogenous serum EPO level had decreased to about 40% compared with that of control rats. Gentamicin-treated rats showed marked elevation of blood urea nitrogen, extensive tubular necrosis in the kidney and haemosiderin deposition in the spleen. In the osmotic fragility test, the fragility of erythrocytes significantly increased compared with that of control rats. These findings indicate that the anaemia induced by gentamicin is due not only to a deficiency of EPO but also to an enhancement of fragility of erythrocytes in an azotaemic environment. The administration of r-HuEPO during anaemia markedly increased red blood cell count, haematocrit and haemoglobin concentration. It is suggested that a gentamicin-treated rat is a useful and convenient anaemic model and r-HuEPO is useful for treatment of anaemia in acute renal failure.

Experimental contrast-associated nephropathy and its clinical implications

Acute renal failure after contrast media injection has been recognized for at least 35 years but the exact mechanism responsible for the renal injury remains an enigma. The clinical characteristics of contrast-induced nephropathy (CAN) are well-known although more recently the nonoliguric presentation has occurred at an increased frequency--in 70 to 90% of cases. For nonoliguric presentation of CAN, one can expect an asymptomatic increase in serum creatinine, the mean peak occurring at 4.2 days. If oliguric, the fractional excretion of sodium will be less than 1% and resistant to either fluid challenge or loop diuretics. Preexisting renal insufficiency, with or without diabetes mellitus, increases the risk of CAN 6- to 10-fold but recovery is expected, with less than 10% of all patients requiring dialytic support. Despite the growing body of published reports, the lack of a suitable animal model to evaluate various proposed mechanisms of renal injury has compromised our ability to devise a technique for preventing CAN. A popular scheme has been proposed to describe the possible sequence by which ischemia or nephrotoxins, or both, induce acute renal failure. In particular, a vascular mechanism (i.e., ischemia), is an appealing explanation for CAN since acute changes in renal hemodynamics after contrast media injection have been confirmed by several animal experiments. Unlike other vascular beds in which contrast media induce acute vasoconstriction followed by vasodilatation, the initial effect on the renal circulation is acute vasodilatation, followed by progressive vasoconstriction, increasing renal vascular resistance and a concomitant decrease in both renal blood flow and glomerular filtration rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Immediate and long-term renal effects of fetal exposure to gentamicin

Aminoglycoside antibiotics, like gentamicin, given to pregnant females cross the placenta and accumulate in the fetal kidney, which, like the adult kidney, was found to be the major site of deposition. In young guinea-pigs whose mothers were given gentamicin during the week following nephrogenesis in the fetus, nephron growth was found to be retarded temporarily. In rats whose mothers were given gentamicin during the period of fetal nephrogenesis, the final number of nephrons was reduced by about 20%. In both cases, renal development was impaired, although the concentration of gentamicin in the fetal kidney was lower than that measured in the kidney of human fetuses whose mothers had received a single injection of aminoglycoside. In rats exposed to gentamicin in utero, cellular damage of the undifferentiated and differentiating renal tissues was observed. It is, there are likely that the oligonephronia observed in animals born of gentamicin-treated mothers resulted from a direct effect of the drug at early stages of nephrogenesis. When gentamicin administration to the mother was prolonged, part of the oligonephronia observed at birth might have also resulted from fetal growth retardation, secondary to adverse effects of the drug on the mother. Providing it was not associated with fetal growth retardation, the presence of high gentamicin concentrations in the fetal kidney at late stages of nephrogenesis did not affect nephron differentiation. Long-term studies of rats born with gentamicin-induced oligonephronia showed that neither the antibiotic still present in kidney several weeks after birth, nor the injuries it caused, prevented renal growth and morphological adaptation of the nephrons to their reduced number.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast-associated nephropathy

Contrast nephropathy can be defined as an acute impairment of renal function that follows exposure to radiocontrast materials and for which alternative explanations for renal impairment have been eliminated. Based on reported studies, the incidence of contrast associated nephropathy (CAN) varies from 0 to 22%. This wide variation can be traced to differences in study design and the criteria used to designate significant renal impairment. Irrespective of the exact incidence, 2 defined risk factors have been identified: preexisting renal disease and diabetes mellitus. Whereas preexisting renal insufficiency is the single most influential risk factor for CAN, when diabetes coexists the incidence approaches 100%. The clinical presentation of CAN is distinct, having a temporal relation between the performance of the contrast study in the high-risk patient and the onset of an increase in serum creatinine levels within the next 24 hours. Serum creatinine values greater than 50% of baseline or rising 1 mg/dl or more is diagnostic. The peak serum creatinine level occurs within 3 to 5 days of the contrast study and oliguria is associated in approximately 30% of the cases. Monitoring serum creatinine is the most useful clinical procedure in high-risk patients after angiography. At least 5 potential pathophysiologic mechanisms of CAN have been proposed: interference with renal perfusion, altered glomerular perm-selectivity, direct tubular injury, intraluminal obstruction, and immunologic mechanisms. Support for each mechanism, either singularly or in combination, can be found in published reports; however, none has achieved universal acceptance. The single most important clinical axiom regarding the prevention and management of CAN is, "Always use the least invasive diagnostic procedure available."(ABSTRACT TRUNCATED AT 250 WORDS)

Acute renal failure

Although a wide variety of disease processes can result in a failure of renal excretory function, the vast majority of cases with "acute renal failure" (ARF) are due to the syndrome of acute tubular necrosis (ATN). The syndrome is usually initiated by an acute injury to the proximal renal tubular epithelial cells by ischemic or nephrotoxic events. This is followed by progressive and often rapid increases in the concentration of blood urea nitrogen (BUN) and serum creatinine. In the average case, the failure of renal excretory function persists for 1 to 3 weeks, to be followed by recovery. Oliguria (urine volume less than 400 ml) is present in about half of the patients. The pathogenesis of the retention of nitrogenous waste in human ATN is the subject of controversy, but the balance of data in most patients suggests that the predominant mechanism is a profound secondary vasoconstriction in response to tubular cell injury. This may represent a teleologically appropriate response to prevent catastrophic losses of fluid that would occur, if the normally high rates of glomerular filtration continued, in the face of reduced tubular reabsorptive capacity. The mechanisms by which the tubular cell injury is communicated to the vasculature, and the mediators of the hemodynamic changes, remain to be established. The differential diagnosis in a patient with ARF, usually involves exclusion of an obstruction to the urinary tract as an initial step. The next step is to differentiate the patients with ATN from those who have renal hypoperfusion in response to events in the systemic circulation, but who otherwise have functionally and structurally intact kidneys, i.e., prerenal ARF. The kidneys of patients with prerenal ARF exhibit the normal renal response to an acute reduction in renal blood flow and glomerular filtration rate (GFR). This consists of avid reabsorption of the filtered salt and H2O, so that a small amount of concentrated and NaCl-poor urine is elaborated. The tubular cell injury in ATN syndromes prevents this response from maximally occurring, so that the urine is isosmotic and relatively rich in NaCl.

Light and electron microscopic characterization of the proliferative response induced by tobramycin in rat kidney cortex

Administration of aminoglycoside antibiotics is frequently associated with tubular necrosis which can eventually lead to renal dysfunction. Previously, we have shown that renal tissue injury due to aminoglycoside nephrotoxicity elicits a process of tissue repair characterized by stimulation of cell proliferation. The present study was undertaken to examine both quantitatively and qualitatively the cell proliferation associated with renal tissue repair. Female Sprague-Dawley rats (180-200 g body weight) were treated ip for 10 days with various doses of tobramycin (10, 20, or 50 mg/kg twice daily). Each animal received 200 microCi [3H]thymidine 1 hr before sacrifice to evaluate the extent of cell proliferation in renal cortex. The rate of DNA synthesis in renal cortex was estimated by measuring the specific radioactivity of the nucleic acid. The frequency and localization of S-phase cells in cortex tissue were determined on paraffin and plastic tissue sections processed for histoautoradiography. In addition, the ultrastructure of proliferating cells was characterized by electron microscopic examination of consecutive ultrathin sections. An excellent correlation (r = 0.993) was found between the rate of DNA synthesis and the frequency of S-phase cells evaluated in rats receiving various doses of tobramycin. The stimulation of cell proliferation involved mostly proximal tubular cells and interstitial cells. The latter cells had the ultrastructural appearance of fibroblasts at various stages of differentiation. Similarly, S-phase cells in proximal tubules were either fully differentiated epithelial cells or immature elements. Taken together, the present experimental data illustrate the capacity of the kidney to trigger complex tissue reactions in response to nephrotoxic injury.

Induction, prevention and mechanisms of contrast media-induced acute renal failure

This study describes the development of an experimental model of reversible acute renal failure following infusion of contrast media radiographic dye. Experiments were also performed to investigate possible methods of prevention as well as examine single nephron mechanisms involved in the pathogenesis of the renal failure. Acute renal failure was consistently produced by indomethacin treatment (18 mg/kg) and an intravenous infusion of contrast media (7 ml/kg) into New Zealand rabbits that had been on a low sodium diet for one week. Glomerular filtration rate (GFR), measured by daily creatinine clearance in unanesthetized animals, was significantly decreased (P less than 0.001) 24, 48, and 72 hours following infusion of the contrast dye. Two weeks after induction of acute renal failure, GFR had returned to control. GFR was unchanged during the same time period when the sodium deprived rabbits were given either indomethacin or contrast media alone. Chronic administration of DOCA (1 mg/kg s.c.) and saline drinking water which increased sodium and solute excretions and decreased plasma renin activity also prevented the decrease in GFR. However, acute infusion of either saline or mannitol, which transiently increased sodium and solute excretions and decreased plasma renin activity, did not protect against the development of acute renal failure. Light microscopy revealed no glomerular or tubular changes and no visible obstruction. Micropuncture experiments were performed on three additional groups of anesthetized rabbits: control, acute renal failure, and recovery. Recovery rabbits were allowed a two week period after renal failure before they were micropunctured.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological alterations in distal and collecting tubules of the rat renal cortex after aminoglycoside administration at low doses

Ultrastructural alterations in the cortical, distal and collecting tubules have been examined in female Sprague-Dawley rats treated with various aminoglycosides in clinical use. Gentamicin, dibekacin (10 mg/kg X day), netilmicin, tobramycin (4 or 10 mg/kg X day) or amikacin (37.5 mg/kg X day) were administered intraperitoneally twice a day over different periods of time, extending from 4 to 14 days. The kidney cortex was examined after 4, 7, 10 or 14 days of aminoglycoside administration by light (semithin sections) and electron microscopy. After 7 or more days of treatment, lysosomes in collecting tubular cells (and to a lesser extent in distal tubular cells) contained concentric lamellar material (myeloid bodies), an ultrastructural alteration typical of drug-induced lysosomal phospholipidosis. Although this alteration appeared qualitatively similar to that observed in proximal tubular cells, it was less conspicuous and occurred later during treatment. In addition, distal tubular cells occasionally showed marked vacuolization and disruption of the basal cell architecture. The possible relationship between these alterations and the urine hypo-osmolality characteristic of aminoglycoside-induced renal dysfunction is discussed.

Acute renal failure

Acute renal failure (ARF) is common among critically ill patients and renal dysfunction is often associated with the multisystem organ failure syndrome. The mortality of ARF remains high but animal data indicate that prevention and early treatment may decrease the morbidity and mortality. This review defines ARF based on urine volume, laboratory parameters, and clinical presentation. The pathophysiology of prerenal, postrenal, and intrinsic ART are differentiated and diagnostic criteria provided. Preventive therapy, supportive care, and proposed treatments are outlined. Studies examining the prevention and treatment of ARF in animal models and trials in humans are evaluated. Mannitol 0.5-1 g/kg, furosemide 0.5-1 mg/kg initially, and dopamine 1-5 micrograms/kg/min are effective in preventing or decreasing the severity of ARF in animal models. In humans these drugs are effective at maintaining urine output in various clinical situations and converting oliguria to nonoliguria in some patients; however, increased survival has not been adequately proven as of yet. Dialysis and experimental therapy are briefly discussed.

Quantitative effects of osmotic diuresis following angiographic contrast administration

Osmotic diuresis resulting from the administration of angiographic contrast poses the potential threat of marked volume losses obligated by the renal excretion of non-reabsorbable solute. We prospectively assessed urinary excretion of solute and water following cardiac angiography in 14 euvolemic subjects without preexisting renal disease, by a protocol that allowed each patient to serve as his own control. During the initial 6 h after the beginning of angiography, contrast administration resulted in increased total osmolar excretion from a control rate of 0.79 +/- 0.09 to 1.09 +/- 0.09 mOsm/min (P less than .05) with a return to control values thereafter. Surprisingly, sodium, potassium, and chloride excretion rates did not differ significantly from control values. After subtraction of the molar contribution of electrolytes, urea, and creatinine from the total osmolar excretion rate, it was apparent that the "residual osmolar excretion rate" of 0.48 +/- 0.05 mOsm/min was markedly elevated over the control value of 0.11 +/- 0.05 mOsm/min (P less than .01), reflecting the excretion of contrast agent. Despite the marked osmotic diuresis, urine output during this period (3.9 +/- 0.2 cc/min) did not differ significantly from the control value of 4.0 +/- 0.3 cc/min. We conclude that marked volume losses are not a necessary concomitant of contrast-induced osmotic diuresis in the euvolemic cardiac patient without renal disease.

Is 125I iothalamate an ideal marker for glomerular filtration?

The triiodinated angiographic contrast medium, iothalamate, has (usually labelled 125I) been used extensively as a marker for glomerular filtration. We have studied the renal handling of 125I iothalamate (IOT) in vivo and in vitro in several species. In renal cortical slices from chicken, rabbit, rat, and monkey, the tissue-to-medium ratio of IOT was twice that of 51Cr-EDTA (EDTA) at 37 degrees C; a difference that was abolished at 0 degree C and markedly reduced by added o-iodohippurate or iodipamide. In five chickens the steady-state renal clearance of IOT (CIOT) was twice (P less than 0.05) that of EDTA (CEDTA) or 3H inulin (C1); a difference that was abolished by administration of 100 mg/kg/hr of novobiocin, an organic anion transport inhibitor. CEDTA was similar to C1 before as well as after transport inhibition. Utilizing the Sperber technique the mean apparent tubular excretion fraction (ATEF) of IOT was 8%, while that of EDTA was 1% (P less than 0.01; N = 10). After novobiocin coinfusion (new steady-state) ATEFIOT was significantly reduced (P less than 0.01) and not different from that of EDTA (-1%). In the same animals the total urinary recovery of IOT was 84 and 57% (P less than 0.01) before and after novobiocin, respectively, while corresponding values for EDTA was unchanged by the inhibitor. In seven rats the renal extraction of IOT was reduced from 29 to 17% (P less than 0.05) by coinfusion of probenecid (5 mg/kg/hr). Corresponding extractions were 82 to 34% (P less than 0.005) and 22% (unchanged) for PAH and EDTA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of some simple manoeuvres on the course of acute renal failure after gentamycin treatment in rats

For a period of 5 days, Wistar rats received Gentamycin (G), 100 mg/kg b.w./day i.m. Three days after the last injection, the rats were sacrificed and the plasma concentrations of urea (PU) and creatinine (PCr) were determined. Both values were significantly higher than in the control rats receiving vehicle only. The increase was substantially greater in females than in males. The rats drinking isotonic NaCl solution instead of water 7 days prior to G showed near normal PU and PCr values; drinking of NaHCO3 had a similar protective effect. Isotonic sucrose solution was without any influence. The rats drinking Ca gluconate or NH4Cl solutions had similar or higher PU and PCr values as rats drinking water, but their body weight and overall condition markedly deteriorated. Brattleboro rats with diabetes insipidus exhibited a very similar course as Wistar rats; there was also no significant difference between the former and their heterozygous non-insipidic litter mates.

Iothalamate stimulates hydroperoxide formation by soybean lipoxygenase

Sodium iothalamate produced a dose dependent increase in basal oxygen consumption when soybean lipoxygenase was incubated with arachidonic acid in 0.1M borate buffer pH 9.0. The increase in oxygen consumption was associated with an increase in absorbance at 234 nm indicating an increased conjugated diene formation. The stimulation of 02 consumption was demonstrated to be due to an increase in 1500H arachidonic formation. The increase in 1500H arachidonate formation could be blocked by mannitol which is an inhibitor of the lipoxygenase enzyme. N-methyl glucamine (meglumine) which is added to some preparations of iothalamate, was also able to suppress the increase in hydroperoxide formation in a dose dependent fashion.

Reduction of renal blood flow and proximal bicarbonate reabsorption in rats by gentamicin

Although aminoglycoside-induced acute renal failure occurs commonly, little is known about the mechanisms which alter renal hemodynamics. In sodium-depleted Sprague-Dawley rats treated with gentamicin, we measured RBF and GFR at the onset of this model of nephrotoxic acute renal failure. After 10 days of sodium chloride depletion, one group of rats received a single injection of gentamicin, 100 mg/kg, while control animals received the gentamicin vehicle. Twenty-four hours later, PCr and UNa/UCr were similar in both groups. CIn was unchanged, but RBF was reduced significantly (12.40 +/- 1.33 vs. 16.89 +/- 1.24 ml/min). Micropuncture studies revealed that although SNGFR was unchanged, end-proximal and early distal flow rates were increased significantly. End-proximal TFCl was reduced significantly in gentamicin-treated animals when compared to controls (130.7 +/- 3.9 vs. 149.5 +/- 4.1 mEq/liter). Early distal TFCl was also reduced significantly (32.4 +/- 2.0 vs. 44.3 +/- 1.4 mEq/liter). In other rats, 24 hr after a second injection of gentamicin, PCr and UNa/UCr were increased significantly and both GFR and RBF were reduced significantly. We conclude that the earliest hemodynamic change in gentamicin-induced acute renal failure is a reduction in RBF which precedes any change in GFR. A single dose of gentamicin also impairs proximal bicarbonate and water reabsorption and reduces end-proximal and early distal chloride concentration.

Intervention in patients with renovascular hypertension and renal insufficiency

We report on 21 severely hypertensive patients with renal artery stenosis and renal insufficiency in whom percutaneous transluminal angioplasty and/or renal artery surgery was done in an effort to lower blood pressure and to preserve renal function. Of 12 patients who underwent angioplasty renal function and blood pressure improved in 3. Of the 9 patients without improvement 4 suffered permanent oliguric renal failure. An operation was performed in 12 patients, 4 after having failed angioplasty (1 was treated at another institution before referral for surgery). Two patients died postoperatively but 10 improved, with followup in 6 exceeding 3 years. This retrospective experience suggests that percutaneous transluminal angioplasty is not likely to supplant an operation in the treatment of patients with atherosclerotic renovascular hypertension and renal insufficiency.

The effect of preoperative arteriography on vascular endothelium and replant survival in rabbit ears

Although contrast media injected during arteriography is known to decrease microcirculatory blood flow and alter oxygen delivery capacity of the red blood cell, its effect on the vascular endothelium is unknown. This experiment was designed to determine if there were any alterations in arterial or venous endothelial anatomy by scanning electron microscopy and whether replant survival was decreased following arteriography. Our results suggest that when the injection pressure of arteriography is carefully controlled, the contrast media used in this experiment has no effect on vascular endothelium in rabbit ears examined 30 minutes and 24 hours after arteriography. Furthermore, the survival rate of replanted rabbit ears is not affected by arteriography 24 hours prior to replantation. We conclude that preoperative arteriography remains a valuable tool in the planning of free composite tissue transfer but, based on this study, cannot rule out mechanical complications of arteriography that may be deleterious to free tissue transfer.