Glycerol-induced hemoglobinuric acute renal failure in the rat. I. Micropuncture study of the development of oliguria

Anaesthesia and the kidney

Applied anatomy and physiology of the kidney are briefly reviewed. This includes an account of renal blood flow, glomerular filtration rate, juxtaglomerular apparatus, renal autoregulation and intra-renal blood flow distribution, tubular transport mechanisms, solute handling in proximal tubule, function of loop of Henle and distal tubule system. This section concludes with a summary of changes in tubule fluid along the length of the nephron. Acute effects of anaesthesia are reviewed in detail. Indirect effects include those on circulatory and sympathetic nervous systems, autoregulation, endocrine systems such as those involving anti-diuretic hormone, adrenaline and noradrenaline, renin-angiotensin and aldosterone. Direct effects of anaesthesia on renal function have now been confirmed both in vitro and in vivo. Delayed direct nephrotoxicity of anaesthetics relates predominantly to methoxyflurane (MOF) and its metabolism to inorganic fluoride. Other factors are MOF dose, genetics, age, enzyme induction, obesity, other nephrotoxic drugs. Clinical implications are presented. Enflurane nephrotoxicity is rare but aetiologic factors are similar to the foregoing. Isoflurane and halothane are not nephrotoxic. A consideration of the influence of anaesthetic management on the incidence and severity of postoperative acute renal failure concludes the review.

Theoretical analysis of pathogenetic mechanisms in experimental acute renal failure

A network thermodynamic model of glomerular dynamics has been employed to determine the degree of change in individual glomerular vascular resistances, hydraulic conductivity and proximal tubule pressure that, singly or in concert, could lower GFR to the degree expected in experimental acute renal failure (ARF). In both the rat and dog, the analysis shows that filtration failure is not achieved until preglomerular resistance (RA) is increased at least twofold or postglomerular resistance (RE) is decreased by 74% or more with all other determinants held at control values. Tubular obstruction alone will not provide failed filtration until tubule pressure is increased to 30 to 40 mm Hg in the rat and 44 mm Hg in the dog. A much smaller change in tubular pressure can contribute greatly to the development of filtration failure, however, when occurring in association with major change in individual vascular resistances. Glomerular capillary resistance must be increased to a value more than twice the normal sum of RA and RE (greater than fivefold in the dog), and glomerular capillary hydraulic conductivity lowered to below 5% of control, as isolated changes, before full filtration failure is approached. There is no reason to believe that most forms of ARF relate to only a single abnormality, however, and the effect of concomitant changes in individual resistances, hydraulic conductivity and proximal tubule pressure on glomerular filtration and blood flow is presented in the text and figures. A possible mechanism by which altered blood viscosity at the efferent arteriole may contribute to ARF is discussed and quantified. The degree of change in any determinant required to exert a given effect on filtration is independent of etiology, thus rendering the results of this analysis equally valid for any other pathological event which causes a significantly reduced GFR in the rat or dog.

Acute renal failure--an integrative discussion of morphologic and functional findings

The ultrastructural alterations at the nephron established in animal experiments, were also confirmed, by means of an electron-microscopic examination, in eight cases of human acute renal failure (ARF). Special consideration was given in this study to single cell alterations, particularly in proximal tubular cells, with emphasis being placed on alterations due to single cell damage in the region of the renal fluid compartments. The ultrastructural alterations of the tubular cells in ARF, suggest serious impairment of the cellular capacity for electrolyte transport and metabolic processes. The shunt paths between the tubular fluid compartment and the functional interstitium, arising from necrosis of the tubular cells or dissolution of the gap or tight junctions, were discussed in terms of their significance for the directional, active transport processes of the tubular cells for sodium chloride and the passive water flow. The morphologic findings were reviewed in light of recent findings on cellular membrane processes and electrolyte transport. A reinterpretation of the morphologic and functional findings in ARF is suggested. This takes into consideration single cell function and the integrity of the renal fluid compartments.

Loss of the glomerular contractile response to angiotensin in rats following myohemoglobinuric acute renal failure

To examine the state of the glomerulus in rats protected from acute renal failure (ARF) by prior insult, we measured the contractile responses of isolated glomeruli to angiotensin II (AII) and dibutyryl cyclic AMP (DBcAMP). In healthy rats, both agents induced a dose-related fall in glomerular diameter (P less than 0.001). Saralasin, the angiotensin antagonist, blocked the glomerular response to AII totally and to DBcAMP partially. Two weeks following ARF induced with 50% glycerol (10 ml/kg, im), azotemia had reversed and the nephrotoxic effect of mercuric chloride (4.7 mg/kg, sc) was blunted, as anticipated. AII did not reduce glomerular size, but the response to DBcAMP was sustained at this time. To determine the specificity of the loss of the glomerular response to AII, we also assessed the effects of an AII infusion (1 microgram/kg/min) on blood pressure and renal blood flow. There was a substantial rise in blood pressure (control, 104 +/- 11.8 mm Hg; AI, 131.0 +/- 5.3 mm HG; P less than 0.001) and fall in renal blood flow (control, 2.45 ml/g per min; AII, 0.81 +/- 0.10 ml/g per min; P less than 0.025). Vascular responsiveness to AII was preserved at a time when glomeruli were totally unresponsive and rats were resistant to ARF. The loss of glomerular contractility may, in part, account for the protection from ARF seen in this model: if so, glomerular abnormalities may play a pathogenetic role.

Prostaglandin synthesis by glomeruli isolated from rats with glycerol-induced acute renal failure

In vitro PG synthesis by glomeruli isolated from rats with glycerol-induced acute renal failure (ARF) was measured by radiometric high performance liquid chromatography after incubation with [14C]arachidonic acid and radioimmunoassay (RIA). The four PGs, 6-keto-PGF1 alpha, TXB2, PGF2 alpha, and PGE2 were each synthesized by glomeruli from both control and treated rats but the synthesis rates were greater after glycerol. This increase was not apparent 1 hour after injection but, at 24 hours, all PGs were produced in greater amounts by glomeruli of treated rats. Thus, we studied PGE2, PGE2 alpha, and TXB2 synthesis by glomeruli at various time intervals after induction of ARF using direct RIA, PGF 2 alpha and TXB2 synthesis were greater only at 24 hours and only in the presence of arachidonic acid, whereas PGE2 synthesis was greater at 24 hours, irrespective of arachidonic acid, but at 48 hours only with arachidonic acid. The stimulatory effect of arachidonic acid was always greater in glycerol-treated than in control rats for these three PGs in the later period, whereas a significant decrease for PGE2 was observed at 1 hour. The late increase in PG synthesis may be due to stimulation of the renin-angiotensin system since it was abolished in rats pretreated for 48 hours with captopril. A late increase in PG synthesis by the papilla of the treated rats also was observed. We concluded that any increase in the glomerular production of vasoconstrictor PGs could contribute to the maintenance of acute renal failure, whereas the early fall in the stimulatory effect of arachidonic acid on PGE2 synthesis could play a role in its initiation.

Glycerol: a review of its pharmacology, pharmacokinetics, adverse reactions, and clinical use

Glycerol is a potent osmotic dehydrating agent with additional effects on brain metabolism. In doses of 0.25-2.0 g/kg glycerol decreases intracranial pressure in numerous disease states, including Reye's syndrome, stroke, encephalitis, meningitis, pseudotumor cerebri, central nervous system tumor, and space occupying lesions. It is also effective in lowering intraocular pressure in glaucoma and shrinking the brain during neurosurgical procedures. Hyperosmolality with rebound cerebral overhydration is of concern, especially in patients with altered blood brain barriers. They may be avoided if glycerol is administered on an intermittent rather than a continuous basis. Intravascular hemolysis does not occur with oral use. When administered intravenously, hemolysis can be minimized by using glycerol 10% in dextrose 5% with normal saline at rates of 6 mg/kg/min or less. However, intravenous doses of 1-2 g/kg every 2 hr can be administered safely in severe cases of elevated ICP. In such patients, glycerol serum concentration, serum osmolality and ICP monitoring are required to optimize glycerol therapy.

Acute renal failure in cardiovascular and other surgical patients

The acute onset of oliguria and azotemia in the postoperative setting may be caused by prerenal or postrenal causes or intrinsic renal damage. The first step in arriving at a diagnosis is to review the history in order to elicit the extrarenal factors. Certain simple laboratory tests are of tremendous value in differentiating these conditions. The development of acute renal failure with renal parenchymal damage usually occurs in the setting of hypotension, sepsis, dehydration, and with exposure to nephrotoxins. Most patients will be excreting scant amounts of isotonic urine containing more than 20 to 30 mEq per liter of sodium. Their urine:plasma creatinine ratio is less than or equal to 20:1 and their urinary sediment reveals many epithelial cells and casts. The condition is usually reversible and the treatment is expectant. However, it is still associated with a high mortality, although the survival of patients with acute renal failure may be substantially higher than previously reported. Early dialysis and nutritional support may play an important role in the improved survival. Patients with nonoliguric acute renal failure have urine outputs that may exceed 2 liters per day. Despite this output they demonstrate a stepwise increase in serum urea and creatinine. Urine sodium and osmolality are not very helpful. Many such patients do have low (less than 20 mEq per liter) urine sodium concentration and excrete isotonic urine.

Clonidine after renal ischemia to lessen acute renal failure and microvascular damage

Clonidine, an antihypertensive drug that inhibits renin release and causes a water diuresis in normal animals, was tested for its ability to reduce the severity of post-ischemic acute renal failure produced in rabbits by clamping the left renal pedicle for 1 hour and removing the opposite kidney. Clonidine significantly lessened renal failure when given during, or 1 hours after, the ischemic insult in dehydrated rabbits. It was also effective when given during the ischemic insult in vasopressin-treated water-drinking rabbits but not in control water-drinking rabbits. In vasopressin-treated rabbits, clonidine lessened renal failure observed 2 days after the ischemic insult despite the fact that in the immediate postischemic period it lowered total renal blood flow, produced hypotension, and did not bring about lower plasma renin levels. Clonidine treatment resulted in less outer medullary microvascular damage (demonstrated by colloidal carbon staining), higher outer medullary blood flow 1 to 2 hours after unclamping, fewer casts, and higher creatinine clearance and free water clearance/creatinine clearance 4 to 6 hours after unclamping compared with controls. The effect of clonidine was unrelated to plasma renin activity. Clonidine did not alter plasma vasopressin concentration. Demeclocycline and lithium, two agents that blunt renal responsiveness to vasopressin, had a beneficial effect in dehydrated animals similar to that of clonidine, but the angiotensin II antagonist saralasin and the angiotensin converting enzyme inhibitor SQ20881 did not. Normal rabbits given a large dose of vasopressin in oil plus clonidine had significantly greater urine output and free water clearance and lower urine osmolality than did rabbits given vasopressin in oil alone. These results suggest that clonidine may be beneficial because it prevents ischemic microvascular injury in the renal outer medulla, an effect that may decrease tubular obstruction by lessening desquamation of damaged tubular cells or cell constituents into the tubular lumen. Clonidine may also decrease formation of obstructive hyaline casts in collecting ducts by blunting the kidney's response to vasopressin and increasing tubular fluid flow rate.

[Toxic nephropathies (author's transl)]

Direct tubular damage, hypersensitivity reaction, metabolically mediated kidney disturbances, and chronic nephropathies are important sequelae of several drugs or their metabolites. In this review the drug-induced kidney disease is discussed from a clinical, histological, and pathogenetic point of view. The knowledge of possible nephrotoxic reactions and their underlying toxins are essential for prevention of this kidney disease.

The effect of clonidine on tubular obstruction in postischemic acute renal failure in the rabbit demonstrated by microradiography and microdissection

Acute renal failure was produced in vasopression-pretreated rabbits by clamping the left renal pedicle for one hour and removing the opposite kidney. Treatment with clonidine, as antihypertensive drug that blunts the kidney's response to vasopressin, resulted in significantly higher creatinine clearance and urine flow rate in the first 6 hours after unclamping. Clonidine (30 microgram/kg given intravenously 30 minutes before unclamping) also significantly lessened the number of hyaline casts in outer medullary tubules and inner medullary loops of Henle 6 hours after unclamping and reduced the number of abnormal tubular contours in microadiograms produced by infusing barium sulfate into the renal artery at sufficient pressure to rupture glomerular capillaries, causing an escape of contrast material into the tubules. The spaces consistently observed between the ends of barium columns and hyaline casts in microdissection studies and the great lengths of the hyaline casts suggest that hyaline casts obstruct the flow of tubular fluid. Clonidine treatment resulted in fewer, shorter, and thinner hyaline casts. These results indicate that tubular obstruction by hyaline casts plays an important role in early postischemic acute renal failure, and that clonidine's beneficial effect is due in part to a reduction in cast formation.

Synergism of dopamine plus furosemide in preventing acute renal failure in the dog

The protective effects of a combination of dopamine and furosemide were studied in dogs during the initial phase of acute renal failure (ARF) induced by intravenous uranyl nitrate (10 mg/kg). Fifteen minutes after injection of the nephrotoxin, and infusion of dopamine (3 micrograms/kg/min), furosemide (1 mg/kg/bolus followed by 1 mg/kg/hr), or both drugs simultaneously were given for 6 hours. Exogenous creatinine clearance was measured for 6 hours, and the intrarenal blood flow was measured with radioactive microspheres before and 3 hours after the induction of ARF. Treatment with both dopamine and furosemide produced renal vasodilatation, high urine flow rate, and attenuation of the fall in GRF seen in untreated animals. In contrast, single use of dopamine or furosemide was totally ineffective in producing renal vasodilation, a diuresis, or the maintenance of the GFR. These data indicate that dopamine plus furosemide have a synergistic effect in preventing the early pathophysiologic changes associated with ARF in this animal model. Maintenance of a high GFR correlated best with the enhancement of solute excretion and urine flow rate. Potential protective effects of dopamine plus furosemide in other models of ARF deserve careful investigation.

Acute renal failure due to non-traumatic rhabdomyolysis

Seventeen patients with acute renal failure of diverse aetiology showed myoglobinuria and elevated levels of serum creatine phosphokinase (mean 119·2 Sigma u./ml) and adolase (mean 88·5 Sibley-Lehninger (SL)u./ml), indicating the presence of diffuse muscle cell injury. The primary conditions which led to rhabdomyolysis and acute renal failure were burns, eclampsia, prolonged labour, crush injury, epileptiform convulsions, status asthmaticus, viral myositis and intoxication with chemicals including copper sulphate, mercuric chloride and zinc phosphide. In 10 non-myoglobinuric patients with acute renal failure, serum creatine phosphokinase was normal (mean 8·9 Sigma u./ml) and serum aldolase was only slightly elevated (mean 11·2 SL u./ml). Although uric acid was elevated in both groups, the values were significantly higher in myoglobinuric (mean 0·728 ± 0·199 mmol/l) compared to non-myoglobinuric patients (mean 0·583 ± 0·093 mmol/l). During the oliguric phase, hypocalcaemia was observed in 82·2% of myoglobinuric patients and in 20% of non-myoglobinuric patients. Ten out of 15 patients with myoglobinuric renal failure developed hypercalcaemia during the diuretic phase whereas only 3 non-myoglobinuric patients showed a transient hypercalcaemia. Although the mean serum potassium was somewhat higher in the myoglobinuric patients, the difference between the 2 groups was not significant. It is concluded that acute renal failure associated with non-traumatic rhabdomyolysis is not infrequent and may occur in a variety of conditions where gross evidence of muscle injury is lacking.

The early phase of experimental acute renal failure. IV. The diluting ability of the short loops of Henle

Experiments were conducted to establish whether diminished solute reabsorption in the loop of Henle during acute renal failure could explain the loss of urinary concentration and participate in generating a tubuloglomerular feedback-mediated reduction in filtration rate. The electrolyte content of the fluid in the ascending limb of the loop of Henle was determined in situ by monitoring its electrical conductivity after propulsion into the distal tubule with a sudden burst perfusion. The value of the minimum electrolyte concentration decreased exponentially with increasing equilibration time, reaching a steady-state value equivalent to 27 +/- 9 mM NaCl in normal kidneys, 34 +/- 15 mM in mercuric chloride kidneys and 53 +/- 22 mM following ischaemia. A mathematical model was derived to describe the process of sodium chloride dilution from which it was possible to calculate both the permeability and transport velocity of the cortical thick ascending limb. In the normal kidney, the transport velocity was calculated to be 4.65 +/- 0.92 . 10(-5) cm/s, a value not significantly different from that of the mercuric chloride of ischaemic kidneys, and the estimated permeability was 1.13 +/- 0.52 . 10(-5) cm/s, not different from that of the mercuric chloride kidneys but significantly lower than that calculated for the ischaemic kidneys. It is concluded that for the more severely damaged ischaemic model, the loss of urinary concentrating ability was accompanied by a reduction in diluting ability of the ascending limb of the short loop of Henle, which appears to be due, at least in part, to an elevation of the passive permeability to sodium chloride in this segment.

[Action of furosemide in experimental acute renal failure (author's transl)]

The action of furosemide was studied in glycerol-induced acute renal failure of rats. Acute renal failure was induced by an intramuscular injection of 50% glycerol (10 ml/kg). A marked increase in plasma urea concentration was found after the glycerol injection. Urea concentration increased to a maximal value of 339 +/- 67 mg/100 ml at the third day after glycerol application. 36% of the animals died within the first 4 days after glycerol. Furosemide (20 mg/kg) was injected intraperitoneally daily and for the first time 24 h after injection of glycerol Mortality and azotemia of acute renal failure was not improved by this drug.

Intrarenal hemodynamics in the transplanted rat kidney

Regional and single glomerular blood flow conditions in the transplanted rat kidney after various periods of cold ischemia were investigated with use of the microsphere method. Intravascular injection of a silicon rubber compound (Microfil) allowed identification and sampling of single glomeruli. The periods of ischemia were two hours (minor damage), 12 hr (intermediate damage), and 16 hr (severe damage). After two hours of cold ischemia, the regional and total renal blood flows were fairly normal. After 12 hr and 16 hr of cold ischemia, the total and regional blood flows were reduced five minutes after recirculation, the reduction being pronounced in the deep cortex and juxtamedullary glomeruli. In the 12-hr group, the blood flow showed complete restitution after 65 min, whereas in the 16-hr group, the blood flow in the inner cortex and juxtamedullary glomeruli remained decreased. An impairment of medullary circulation would seem to be an important component in the pathophysiology of acute renal failure in this model.

The early phase of experimental acute renal failure. III. Tubologlomerular feedback

Experiments were designed to determine whether tubologlomerular feedback, which modifies nephron filtration rate in response to alterations in the macula densa sodium chloride concentration, was still apparent in the initiation phase of various types of acute renal failure. The response of the glomerulus to changes in the macula densa stimulus was evaluated in haeme pigment, ischaemic and nephrotoxic induced renal damage by measuring early proximal flow rates. The sodium chloride concentration at the macula densa was varied between low values and isotonicity in two ways: firstly, by interruption of flow through the loop of Henle, followed by orthograde perfusion with Ringer's solution; secondly, by retrograde perfusion of the loop of Henle with isosmotic mannitol or Ringer's solution. In all nephrons examined, filtration rate was inversely correlated to the macula densa sodium chloride concentration, except during orthograde perfusion with 10(-4) M furosemide in Ringer's solution, when, despite the high sodium chloride concentration, filtration rate remained high. It is concluded that the mechanism of tubuloglomerular feedback is viable after the onset of compromised renal function, and may, as postulated, account for the reduction in blood flow and nephron filtration rate occurring in acute renal failure.

Action of the competitive angiotensin II antagonist saralasin during the initial phase of glycerol-induced acute renal failure of the rat

The effects of the competitive angiotensin II antagonist saralasin (1-sarcosine-8-alanine-5-isoleucine-angiotensin II) on renal function in healthy rats and in rats with myohemoglobinuric acute renal failure were studied. Acute renal failure was induced by an intramuscular injection of 50% glycerol (10 ml.kg-1). Functional impairment of the glycerol treated animals consisted in a decrease of renal blood flow (electromagnetic flowmeter) and GFR and in an increase of urine volume and arterial blood pressure. In healthy rats saralasin (6 microgram.kg-1.min-1 i.v.) had no renal effects by itself but antagonized the angiotensin II (200 ng.kg-1.min i.v.) induced fall of renal blood flow and GFR and the increase of arterial blood pressure. Given to glycerol treated animals saralasin did not induce any change of arterial blood pressure, renal blood flow, GFR or the urinary excretion of fluid and sodium.

The early phase of experimental acute renal failure. I. Intratubular pressure and obstruction

Tubular obstruction in acute renal failure, postulated to cause the restricted excretory function, is suggested by raising intratubular pressure, to lower effective filtration pressure and diminish urine output. To examine the applicability of the obstruction hypothesis to the pathogenesis of experimental acute renal failure, proximal intratubular pressure and renal function were measured after renal insults of different origins and severity. Obstruction in acute renal failure kidneys should manifest itself as an increase in intratubular pressure for a least 12 h, for within this time period following ureteral occlusion, elevated pressures were found to reflect obstruction. The consistent existence of raised proximal intratubular pressure in acute renal failure kidneys could not be detected; ischaemic and nephrototoxic models were found in which no rise in intratubular pressure could be demonstrated. The oliguric nature of acute renal failure kidneys could not be verified; ischaemic and nephrotoxic models were found in which urine output was either normal or enhanced. Only for methaemoglobin induced renal failure were raised intratubular pressure, oliguria and casts concurrent. It is concluded that obstruction is not a consistent feature of experimental acute renal failure and that the obstruction hypothesis may be specifically applicable to only a few models, which include haeme pigment and folic acid induced renal failure.

Acute renal failure in the neonate

With advances in diagnostic technology, the diagnosis of renal failure from prerenal and renal causes is being made more frequently. With better clinical understanding of etiologic causes, early prevention and diagnostic and therapeutic measures can be taken. Proper and controlled use of fluids, calories, and drugs is essential. Because of its relative ease, peritoneal dialysis is usually preferred over hemodialysis when renal failure cannot be handled more conservatively. Although the incidence of renal failure has apparently increased with the advent of neonatal intensive care, survival rates are increasing and the potential for prevention is better.

Crush syndrome: a report of 2 cases and a review of the literature

The crush syndrome was first defined as a clinical entity in 1941. This paper reports 2 patients suffering from the syndrome as a result of being trapped for several hours during the Moorgate tube train disaster. An account of the initial course, management and complications is presented and discussed with reference to the available literature on the subject.

Normal renocortical blood flow in experimental acute renal failure

Renal cortical blood flow of rats with postischemic, myohemoglobinuric, and mercury-induced acute renal failure was measured by the hydrogen washout technique using implanted platinum electrodes. Total renal blood flow was determined by venous cannulation in separate series of rats. The values obtained with the two methods were in excellent qualitative agreement (r=0.99, P less than 0.001), although venous cannulation gave values that were constantly lower than those calculated for whole kidney from the cortical flow rate and assumed cortical mass. Myohemoglobinuria produced by glycerol injection caused cortical blood flow to fall from a control value of 7.37+/-0.23 (SEM) ml/min X g of cortex to approximately one-half that value for four hours after injection (P less than 0.001). Flow rates 12 and 24 hr after glycerol injection were 85% (P less than 0.001) and 90% (P less than 0.05) of control, respectively. Cortical flow was reduced to 5.49+/-0.39 (SEM) ml/min X g of cortex four hours after release of one hour's total bilateral renal arterial occlusion (P less than 0.001), but rose to normal within 24 hr. Poisoning with 4.7 mg/kg of body wt of mercuric chloride produced a cortical blood flow value that was 30% higher than control 24 hr after injection (P less than 0.01), while a 12 mg/kg of body wt dose gave a normal flow value. Inulin clearance was severely depressed in all models at all study times. Thus, in contrast to human acute renal failure, marked renal cortical ischemia is not an essential feature of these different forms of murine acute renal failure.

The effect of indomethacin blockade of prostaglandin synthesis on blood pressure of normal rabbits and rabbits with renovascular hypertension

Indomethacin inhibits the synthesis of prostaglandin and the release of renin. These effects were studied in normal rabbits and rabbits with two-kidney Goldblatt hypertension (2KGH) and one-kidney Goldblatt hypertension (1KGH) by giving daily intravenous injections of indomethacin (3mg/kg after two initial doses of 9 mg/kg), and in appropriate control rabbits given diluent phosphate buffer without indomethacin. In normal rabbits, indomethacin significantly decreased immunoreactive plasma prostaglandin E-like substance (IPGE) and plasma renin activity (PRA). Indomethacin did not change plasma creatinine (PCr) or mean blood pressure but it decreased renal blood flow (RBF) and glomerular filtration rate (GFR). In 2KGH rabbits, responses depended on the level of renal function and, to a lesser extent, on the level of PRA. In six of10 2KGH rabbits in which hypertension developed without significant changes in PRA, IPGE, PCr, RBF, and GFR, indomethacin produced changes similar to those seen in normals. In the other four rabbits, development of 2KGH was accompanied by increased PRA, increased IPGE, and decreased RBF and GFR, and indomethacin produced renal failure, oliguria, malignant hypertension, and death within 5 days. In 1KGH rabbits, indomethacin decreased IPGE, PRA, and renal function but increased mean blood pressure. These observations suggest that prostaglandins exert a protective effect on renal function in renovascular hypertension.

Renal hemodynamics in uranyl acetate-induced acute renal failure of rabbits

The role of renal hemodynamic alterations in the curtailment of renal function was studied in rabbits with uranyl acetate-induced acute renal failure. The day following the i.v. injection of uranyl acetate (2 mg/kg of body wt), renal blood flow (RBF) and clearance of creatinine (Ccr) decreased to approximately 60 and 20% of controls, respectively. Intracortical fractional flow distribution, estimated by radioactive microsphere method, did not change. The extraction ratio of para-aminohippurate (EPAH) decreased and the renal extraction of sodium (CNa/Ccr) increased, with minimal structural change in the kidney. Urine output increased to two to three times that of the control. After three days oliguria appeared despite complete recovery of RBF. The zonal flow redistributed toward the deep cortex. CCr and EPAH reached their minimums, concomitantly with tubular necrosis and intratubular casts. After seven days animals could be divided into the oliguric and diuretic groups. CCr and EPAH were higher in the diuretic group, while there was no significant difference in RBF and the flow distribution between groups. Regeneration of damagee tubular cells was found in the diuretic group but not in the oliguric group. The findings suggest the minor roles of RBF and the intracortical flow distribution, and a fundamental role of back leakage of filtrate across damaged tubular epithelium in the maintenance of reduced CCR and urine output during the oliguric stage in rabbits with uranyl acetate-induced renal failure.

Effect of variation in dietary NaCl intake on total and fractional renal blood flow in the normal and mercury-intoxicated rat

We studied the effect of different chronic (3-4 weeks) dietary salt intakes on intrarenal hemodynamics of normal and mercury-intoxicated rats. Cardiac output (CO), total renal blood flow (RBF), and the zonal perfusion rate in the outer cortex (OC) and inner cortex (IC) were measured by the radioactive microsphere method. The distribution of cortical blood flow was calculated as the distribution index (DI), which reflects the ratio OC/IC. Rats were placed on a high salt diet (group I), intermediate salt diet (group II), or low salt diet (group III). For each group control rats (subgroup A) and mercury-intoxicated rats (subgroup B) were studied. No effect of the different salt intakes on the DI could be detected. The DI in group IA was 2.35 +/- 0.14; in IIA, 2.40 +/- 0.16; and in IIIA, 2.38 +/- 0.09 (P greater than 0.05). After mercury injection RBF changed from 5.32 +/- 0.36 ml/g.min(-1) (IIA) to 3.31 +/- 0.20 ml/g.min(-1), IIB and from 4.32 +/- 0.11ml/g.min(-1) (IIIA) to 1.98 +/- 0.10 ml/g.min(-1) (IIIB) P less than 0.01). The DI was lowered to 1.53 +/- 0.06 (IIB) (P less than 0.05) and to 1.16 +/- 0.10 (IIIB) (P less than 0.01). In both IIB and IIIB a marked elevation of the blood urea was noted (IIB = 97 +/- 9 MG/100 ML AND IIIB = 182 +/- 25 mg/100 ml). In group IB no effect on RBF, OC, IC, or DI could be observed (for all values, P greater than 0.05) despite similar histological renal lesions. Group IB rats also had normal blood urea levels (31 +/- 6 mg/100 ml;P greater than 0.05). We conclude (1) that variations in dietary salt intake appear to have no detectable effect on the intracortical blood flow distribution; and furthermore (2) that the mercury-induced acute renal failure (ARF) is characterized hemodynamically by a total renal and preferential outer cortical ischemia and that chronic salt loading prevents the ARF while preserving normal renal perfusion.

Renal effects of furosemide in glycerol induced acute renal failure of the rat

The renal effects of furosemide in acute renal failure of the rat were studied using clearance and micropuncture techniques. Acute renal failure was induced by an intramuscular injection of 50% glycerol (10 ml/kg). Functional impairement of the glycerol treated animals consisted of a decrease in urinary sodium excretion, renal blood flow, total kidney GFR and effective filtration pressure of superficial nephrons. Effective filtration pressure was calculated from proximal free flow and stop flow pressure measurements. In contrast to control animals furosemide did not increase urine volume during acute renal failure due to a marked fall in GFR. Renal blood flow, as measured by an electromagnetic flowmeter, also decreased after furosemide in glycerol treated rats and increased in control animals. Furosemide reduced effective filtration pressure during acute renal failure to almost zero, whereas in control animals effective filtration pressure virtually remained constant.

The vascular basis for acute renal failure in the rat. Preglomerular and postglomerular vasoconstriction

Myohemoglobinuric acute renal failure (ARF) was induced in dehydrated, salt-deficient, salt-loaded, and untreated rats by intramuscular injection of glycerol, and the renal vasculature was studied after 24 hours. Kidneys were prepared for examination by rapid freezing in vivo to -160 degrees C and freeze substitution in -80 degrees C alcohol, and by perfusion fixation with 1% glutaraldehyde in Ringer's solution at 120 mm Hg. Frozen kidneys were examined by light microscopy after paraffin and epoxy resin embedding. Techniques used in examining the perfusion-fixed kidneys were: (1) vascular injection with silicone rubber and clearing in glycerol, (2) electron microscopy, and (3) morphometric evaluation of lumen to wall area ratios of glomerular arterioles. Kidneys of all rats with ARF showed renal cortical arterial and glomerular arteriolar (afferent and efferent) vasoconstriction. The degree of constriction, estimated by lumen to wall ratios, correlated with the degree of azotemia (r = -0.71; P less than 0.001). Differences between all ARF groups and respective controls were highly significant (P less than 0.001). Vasoconstriction was maximal in the dehydrated group, intermediate in the untreated and Na-deficient rats, and lowest in the salt-loaded animals. Glomerular and peritubular capillaries were patent and free of endothelial swelling or thrombi. Glomerular basement membranes and epithelial foot processes showed no morphological alterations. The observations suggest that marked pre- and postglomerular vasoconstriction occurs in established myohemoglobinuric ARF, that it is related to azotemia, and that mechanical vascular obstruction does not play a major role in this experimental model.

Renal cortical blood flow in glycerol-induced acute renal failure in the rat

Renal hemodynamics and renal function were evaluated in rats at 3, 24, and 48 hours and at 7 days after the induction of acute renal failure (ARF) by glycerol injection. Three hours after induction of ARF, creatinine clearance was 0.04 ml/min/100 g; renal blood flow (RBF), 1.99 ml/min/100 g; and filtration fraction, 3.7%. All were abnormally low. Although the administration of isotonic saline (total dose, 3% of body weight) to rats 3 hours after glycerol injection significantly improved creatinine clearance (0.17 ml/min/100 g), RBF (2.54 ml/min/100 g), and filtration fraction (12.9%), these values still were significantly lower than those of controls (creatinine clearance = 0.50 ml. ml/min/100 g, RBF = 4.92 ml/min/100 g, filtration fraction = 20.0%, all P values less than 0.001). Serum creatinine concentrations were significantly elevated at 24 hours (3.72% gm/100 ml), 48 hours (4.69 mg/100 ml), and 7 days (0.66 mg/100 ml) after glycerol injection compared to control (0.46 mg/100 ml, all P less than 0.01). RBF during these phases was not different from normal (4.41 ml/min/100 g). RBF 3 hours after bilateral ureteral obstruction was measured to determine the effects of tubular obstruction on renal hemodynamics. The RBF of rats with ureteral obstruction (4.12 ml/min/100 g) was not significantly different from controls (4.41 ml/min/100 g), suggesting that tubular obstruction in this model of ARF is probably not the cause of decreased RBF. The depressed glomerular filtration, as reflected by the decreased creatinine clearance that occurs during glycerol-induced ARF, is probably related to altered intrarenal vascular resistance or to changes in glomerular capillary permeability, or both.

Pathophysiology of a nephrotoxic model of acute renal failure

Studies were performed in the dog to determine the mechanism of the renal functional impairment which follows the administration of the nephrotoxic agent, uranyl nitrate. In the first series of 28 experiments, total renal blood flow was determined with the radioactive microsphere method before and after uranyl nitrate administration, 10 mg/kg. Total blood flow fell from 199 to 121 ml/min 6 hr after administration of uranyl nitrate (P less than 0.001) but was unchanged 48 hr after administration of the drug. Yet the blood urea nitrogen concentration had increased from a control value of 13 to 120 mg/100 ml at 48 hr (P less than 0.001). Since renal blood flow was normal at 48 hr, micropuncture studies were performed to further evaluate the mechanism of the renal impairment. In the first group of nine studies using a 10 mg/kg dose of uranyl nitrate, nephron glomerular filtration rate (GFR) was reduced 37% while total kidney GFR averaged less than 1% of normal. A similar disparity between superficial and total GFR was noted after a 5 mg/kg dose even though urine flow was comparable to values found in normal hydropenic dogs. Proximal tubular transit time and intratubular pressure were normal. The recovery of 3H-inulin injected into the proximal tubule was 97% in normal dogs and 14% in uranyl nitrate dogs (P less than 0.001). Since there was no difference between early and late proximal tubular nephron GFR, it was suggested that the pars recta, the segment most severely involved histologically, was the main site of inulin leak. Scanning electron microscopy revealed an alteration in epithelial architecture which may have accounted, at least in part, for the diminution in nephron GFR. These studies are interpreted to indicate that the impairment in renal function in this model is due to both leakage of filtrate across damaged tubular epithelium and a modest decrease in nephron GFR.

Indomethacin enhancement of glycerol-induced acute renal failure in rabbits

Seventy-three rabbits (2 to 3 kg in weight) were studied during a control period and after receiving 50% glycerol (G) or mercuric chloride (M) with or without indomethacin (I) (controls received the diluent used for I). Plasma creatinine, plasma renin activity, blood pressure, sodium and potassium concentrations, hematocrit value, urinary output, body wt and histologic appearance of the kidney were determined. I enhanced the incidence and severity of the acute renal failure produced by G but failed to aggravate that produced by M. Because the dose of I used in this study blocked the synthesis of renal prostaglandins in the rabbit, we suggest that renal prostaglandins protect against the development of G-induced acute renal failure (a circulatory type of renal failure) in this animal model. Furthermore, the failure of I to aggravate M-induced acute renal failure indicates that it is unlikely that I aggravates G-induced acute renal failure by a direct nephrotoxic effect. No evidence was found for other possible side actions of I being responsible for the observed aggravation.

The mechanism of acute renal failure after uranyl nitrate

Administration of 25 mg/kg uranyl nitrate (UN) to rats leads to a brief period of polyuria followed by progressive oliguria with death at 5 days. Factors that determine glomerular filtration rate (GFR) were examined in control Munich-Wistar rats (n equals 16) and 2 h after either 15 mg/kg (n equals 8) or 25 mg/kg (n equals 7) of UN (i.v.) utilizing direct measurements of hydrostatic and oncotic pressures and plasma flow. Total kidney GFR was reduced to 47% of control in the low dose group and to 21% in the high dose group. The simultaneous nephron filtration rate (sngfr) was 28.6 plus or minus 0.8 nl/min/g kidney wt in control, 29.1 plus or minus 1.0 in the low dose group, and 18.1 plus or minus 1.2 (P less than 0.001) in the higher dose group. This disparity in UN effect upon GFR and sngfr was due to tubular back-diffusion of solute through damaged epithelia beyond the early proximal tubule as demonstrated by microinjection of inulin and mannitol in the proximal tubule. Inulin "leak" persisted at 6 h after UN when tubular pressure had returned to normal. Comparison of sngfr measured in early vs. late proximal tubule revealed no difference after high dose UN, suggesting no significant leak of inulin from the early proximal tubule, and that the decreased sngfr was due to primary reductions in ultrafiltration. Nephron plasma flow was equal to control at both doses of UN. Also directly measured hydrostatic pressure gradient across the glomerular capillary was not changed. The effective filtration pressure achieved equilibrium in control of animals but became significantly positive at the efferent end of the capillary at both doses of UN and increased. Total glomerular permeability (LpA) was progressively reduced from control (0.089 plus or minus 0.005 nl/s/g kidney wt/mm Hg) at low dose UN (0.047 plus or minus 0.013) and high dose 0.024 plus or minus 0.003 nl/s/g kidney wt/mm Hg). Therefore UN decreases GFR by two mechanisms: (1) tubular damage leading to back-diffusion of solutes and (b) a primary reduction in sngfr due to reduced LpA.

Active and passive immunization to angiotensin in experimental acute renal failure

A number of studies support, and others fail to support, the concept that the renin-angiotensin system plays a key role in the pathogenesis of acute renal failure. This study, employing active and passive immunization against angiotensin II, was designed to examine the primacy of circulating angiotensin as a mediator of this syndrome. Neither mode of immunization significantly affected the degree of azotemia or the marked reduction of inulin clearance expected in rats subjected to glycerol-induced myohemoglobinuria. Twenty-four hours after challenge, inulin clearance (Cin) in actively immunized rats fell to 3.2% of control and that of unimmunized rats given the same dose of glycerol was 2.5% of control. Although there was some variation among groups of passively immunized rats, Cin of one group being 18% of control, Cin of the other groups was less than 3% of control. The dose and binding capacity of the immune globulin used here were essentially the same as those reported in another study in which immunization was thought to be of prophylactic value in rats subjected to s.c. administered glycerol injections. Technologic differences unrelated to immunization are suggested to have caused the difference in results in the two studies, and it seems doubtful that circulating angiotensin plays a key role in the pathogenesis of myohemoglobinuric acute renal failure in the rat.

Studies of the mechanism of oliguria in a model of unilateral acute renal failure

To further evaluate the mechanism of the oliguria of acute renal failure, a model was utilized in which intense and prolonged vasoconstriction produced the unilateral cessation of urine flow. The radioactive microsphere method was used to measure total and regional blood flow before and after the intrarenal infusion of norepinephrine, 0.75 mug/kg/min, for 2 h in the dog. In the control kidney, renal blood flow increased 32% 48 h after norepinephrine in association with a fall in the fractional distribution of flow to the outer cortex. In the experimental kidney, total renal blood flow fell from 190 ml/min before norepinephrine to 116 ml/min at 48 h (P < 0.025) with a uniform reduction in cortical blood flow. After the administration of 10% body wt Ringer's solution, there was a marked redistribution of flow to inner cortical nephrons in both the control and experimental kidney. In addition, there was a marked increase in total blood flow in both kidneys. On the experimental side, flow rose to 235 ml/min, a value greater than in either the control period (P < 0.05) or at 48 h after norepinephrine (P < 0.001). However, in spite of this marked increase in blood flow, there was essentially no urine flow from the experimental kidney. In separate studies, the animals were prepared for micropuncture. In all studies, the surface tubules were collapsed, and there was no evidence of tubular obstruction or leakage of filtrate. Over 99% of the 15-muM spheres were extracted in one pass through the experimental kidney. An analysis of the forces affecting filtration suggested that an alteration in the ultrafiltration coefficient may be responsible, at least in part, for the anuria in this model. In this regard, transmission and scanning electron microscopy revealed a marked abnormality in the epithelial structure of the glomerulus. It is suggested that a decrease in glomerular capillary permeability may be present in this model of acute renal failure.