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G J Kaloyanides

Publications and source records attributed to G J Kaloyanides.

At least 37 records · Page 2Linked to original sources
PubMed1985

Effect of gentamicin on lipid peroxidation in rat renal cortex.

We examined the hypothesis that lipid peroxidation participates in the pathogenesis of aminoglycoside-induced nephrotoxicity. Male Sprague-Dawley rats were injected subcutaneously with gentamicin, 100 mg/kg per day, for 1-4 days. Twenty-four or forty-eight hours after the last injection the rats were killed and the renal cortex was processed for total phospholipids, malondialdehyde (MDA), phospholipid fatty acid composition, superoxide dismutase, catalase and glutathione. Gentamicin induced a significant increase in total renal cortical phospholipids which was evident after a single injection and by the third injection reached a plateau 17% above the baseline level. MDA, an end product of lipid peroxidation, increased from 0.674 +/- 0.021 nmole/mg protein in the control group to 0.931 +/- 0.053 nmole/mg protein (P less than 0.001) 48 hr after the fourth injection. As another index of lipid peroxidation, we determined the shift from polyunsaturated to saturated fatty acids of renal cortical phospholipids. By the second injection of gentamicin we detected a significant decline of arachidonic acid (20:4) present in phospholipid. By the fourth injection, arachidonic acid had fallen 48% below control and was accompanied by reciprocal increases of more saturated fatty acids including linoleic (18:2), oleic (18:1) and palmitic (16:0) acids. The number of double bonds per mole of fatty acid declined from a baseline value of 1.62 +/- 0.01 to 1.20 +/- 0.02 (P less than 0.001) by the fourth injection of drug. Superoxide dismutase showed no consistent alteration, whereas catalase activity (k) fell from the control value of 0.221 +/- 0.007 min to 0.155 +/- 0.009 min (P less than 0.01) by the third injection, where k is the first-order rate constant. Total and reduced glutathione declined after the fourth injection of gentamicin accompanied by a shift to oxidized glutathione with an increase in the ratio of oxidized to total glutathione. These data support the conclusion that accelerated lipid peroxidation occurs early in the course of gentamicin administration and raise the possibility that lipid peroxidation is a proximal event in the injury cascade of gentamicin nephrotoxicity.

Animals↗
PubMed1985

Contrasting effects of gentamicin and mercuric chloride on urinary excretion of enzymes and phospholipids in the rat.

Gentamicin induces a phospholipiduria in the rat. We sought to determine whether the phospholipiduria reflected shedding of brush border membrane by measuring the urinary excretion of membrane marker enzymes, by defining the composition of the urinary phospholipids, and by examining the renal cortex and urinary sediment using transmission electron microscopy of rats injected with gentamicin sulfate (100 mg/kg of body weight for 1 to 6 days). The results were compared and contrasted with those of rats injected with mercuric chloride, a nephrotoxin known to cause selective injury to the brush border membrane. Gentamicin-injected rats exhibited a phospholipiduria that by the third day was 10-fold above the baseline level. In contrast the brush border membrane enzymes alanine aminopeptidase and gamma-glutamyl transferase and the lysosomal enzyme N-acetyl-beta-glucosaminidase increased less than 1-fold above baseline. Electron microscopy of the renal cortex revealed the presence of myeloid bodies within lysosomes of proximal tubule cells and lying free within the lumen. The brush border membrane was largely intact. The urine sediment was dominated by the presence of myeloid bodies; there was little evidence of brush border membrane fragments. The urinary phospholpids were enriched in phosphatidylinositiol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. This pattern is similar to that of a lysosomal fraction enriched in myeloid bodies. Rats injected with mercuric chloride exhibited a phospholipiduria associated with sharp increases (7- to 15-fold) in the urinary excretion of brush border membrane enzymes, whereas N-acetyl-beta-glucosaminidase increased less than 3-fold. Electron microscopy revealed blebbing of the apical membrane with loss of microvilli of proximal tubular cells particularly evident along the pars recta. The urinary sediment contained microvilli and fragments of plasma membrane but no myeloid bodies. The urine contained large quantities of sphingomyelin. In the rat renal cortex the brush border membrane is the major source of this phospholipid. We conclude that the phospholipiduria induced by mercuric chloride is derived primarily from the shedding of brush border membrane fragments into the urine. In contrast, the urinary excretion of phospholipid induced by gentamicin reflects primarily the extrusion of the lysosomal myeloid body from proximal tubular cells. We speculate that the origin of the phospholipids making up the lysosomal myeloid body may be the endocytic vesicle that mediates the transport of aminoglycosides into the lysosomal system.

Aminopeptidases↗
PubMed1985

Effect of netilmicin on the phospholipid composition of subcellular fractions of rat renal cortex.

The purpose of this study was to determine the subcellular site(s) of the renal cortical phospholipidosis induced by aminoglycosides. For this purpose we injected male Sprague-Dawley rats s.c. with netilmicin, containing tracer quantities of [3H]netilmicin, at 100 mg/kg/day for 2 days; control rats were injected with saline. Twenty-four hours after the second injection of drug the rats were sacrificed and the renal cortex was fractionated by differential ultracentrifugation and Percoll gradient density techniques to obtain purified lysosomes, mitochondria, microsomes, brush border membranes and basolateral membranes. The total phospholipid content of the renal cortex was 300 +/- 5 nmol/mg of protein in control rats and 340 +/- 5 nmol/mg of protein in netilmicin-injected rats. The total phospholipid content of the lysosomal fraction of netilmicin rats, which was enriched in myeloid bodies and [3H]netilmicin, was 91% greater than that of control rats and reflected significant increases of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol. This pattern is identical to that reported previously for the rat renal cortical phospholipidosis induced by aminoglycosides. The total phospholipid contents of the mitochondrial, microsomal, brush border membrane and basolateral membrane fractions of netilmicin-injected rats were higher by approximately 10% than the respective fractions of control rats and each fraction exhibited a significant increase of one or more of the four phospholipids elevated in the renal cortical homogenate and in the lysosomal fraction. The data indicate that the myeloid body is the primary source of the lysosomal phospholipidosis induced by netilmicin which provides support for the hypothesis that the lysosomal phospholipidosis is secondary to aminoglycoside-induced inhibition of phospholipid degradation. In addition the findings of increased phospholipid content and altered phospholipid composition of the other subcellular fractions raise the possibility that aminoglycoside antibiotics cause a more generalized disturbance of phospholipid metabolism characterized by altered synthesis as well as degradation in renal proximal tubular cells.

Acetylglucosaminidase↗
PubMed1985

[3H]netilmicin binding constants and phospholipid composition of renal plasma membranes of normal and diabetic rats.

We examined the hypothesis that the decreased renal accumulation of aminoglycosides in rats with streptozotocin-induced diabetes mellitus is due to decreased membrane binding of drug consequent to reduced membrane content of the putative aminoglycoside receptor, phosphatidylinositol. Renal brush border membrane (BBM) and basolateral membrane (BLM) vesicles were prepared from normal and diabetic Sprague-Dawley rats by differential centrifugation and Percoll gradient techniques which yielded relatively pure membrane fractions as assessed by measurements of marker enzymes and by electron microscopy. Binding of [3H]netilmicin to plasma membranes was performed using a fast filtration technique. Scatchard analysis of the binding data indicated that netilmicin bound to a single class of receptors on BBM and BLM from normal rats with an affinity constant of 33 +/- 2 X 10(3)M-1 and 23 +/- 2 X 10(3)M-1, respectively. The maximal binding capacity of BLM (70 +/- 4 nmol/mg of protein) was significantly greater (P less than .01) than that of BBM (38 +/- 1 nmol/mg of protein). The affinity constants and maximal binding capacities of BBM and BLM from diabetic rats were not significantly different from those of normal rats. Moreover, 2 days of gentamicin injections at 100 mg/kg/day for 2 days had no appreciable effect on these binding parameters in either group. In control rats the total phospholipid content of BLM (785 +/- 19 nmol/mg of protein) was significantly greater (P less than .01) than that of BBM (592 +/- 19 nmol/mg of protein) and reflected significantly greater quantities of sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Aminoglycoside-induced functional and biochemical defects in the renal cortex.

The first site of aminoglycoside-cell interaction occurs at the plasma membrane of renal proximal tubular cells which have been shown to selectively transport and accumulate these drugs. Depression of apical membrane transport of organic base, low-molecular-weight protein, and glucose, together with loss of brush border membrane enzymes and phospholipids in the urine which results in altered phospholipid composition of this membrane, occurs early in the course of aminoglycoside administration. Less well appreciated are the alterations which occur at the basolateral membrane. These include decreased transport of organic bases, Ca2+, Na2+, and K+; increased organic acid transport; decreased activity of Na+-K+ ATPase and adenylate cyclase; decreased calcium content; and altered phospholipid composition. Many of these changes are evident within 90 min of a single injection of drug. Lysosomal dysfunction is manifested by the accumulation of phospholipids in the form of myeloid bodies consequent to the inhibition of lysosomal phospholipases by aminoglycosides. Labilization of lysosomes in vivo has been postulated to be a mechanism of cell injury. Mitochondrial dysfunction attributed to aminoglycosides includes impaired respiration, inhibition of Mg2+ binding, inhibition of Ca2+ uptake, increased permeability to monovalent cations, decreased ammoniagenesis, and decreased gluconeogenesis. However, it remains unclear how the drug gains access to mitochondria in vivo in order to initiate the functional derangements. It is evident that aminoglycosides cause multiple metabolic derangements at multiple sites within renal proximal tubular cells. At present the available evidence does not identify which, if any, of these drug effects is responsible for initiating the injury cascade. The strong possibility exists that aminoglycoside nephrotoxicity reflects the net impact of multiple minor metabolic derangements which individually are of little significance but when added together seriously compromise the cell's ability to maintain its structural and functional integrity.

Aminoglycosides↗
PubMed1984

Renal transport of netilmicin in the rat.

We examined the renal transport of [3H]netilmicin in the rat using clearance, microinjection and free flow micropuncture techniques. Netilmicin was constantly infused at rates ranging from 1.92 to 192 nmol/min and resulted in plasma concentrations of 0.4 to 40 micrograms/ml and fractional excretion rates of 94.5 +/- 3.3 to 107.9 +/- 1.7%. Although the mean fractional excretion rate of netilmicin was equal to or exceeded the filtered load, the drug continued to accumulate in renal cortex albeit in a curvilinear manner and at the highest rate of infusion attained a peak level of 447 +/- 26 nmol/g of renal cortex. The renal cortical uptake of netilmicin was inhibited in a dose-dependent fashion by the simultaneous infusion of gentamicin. In response to microinjection of [3H]netilmicin (390 +/- 56 pg) 82.0 +/- 1.8% of the dose was recovered in the urine after early proximal tubular injections, 90.5 +/- 1.1% of the dose was recovered after late proximal tubule injections and 98.5 +/- 1.3% of the dose was recovered after early distal tubule injections. In free flow micropuncture experiments the fractional delivery of netilmicin to the early proximal tubule measured 1.16 +/- 0.03, a value significantly greater than 1.0 (P less than .005). No significant change in fractional delivery was evident to the late proximal tubule (1.13 +/- 0.04), whereas it decreased to 1.02 +/- 0.04 (P less than .01) at the early distal tubule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Renal parenchymal malakoplakia presenting as acute oliguric renal failure.

A 47-year-old chronic alcoholic white male with previously normal renal function and no prior history of urinary tract infection developed the sudden onset of fever, bilateral flank pain, oliguria, and deterioration of renal function. Subsequent workup revealed massive pyuria, bilaterally enlarged kidney, and positive urine and blood cultures for E. coli. In spite of successful treatment with appropriate antibiotics and gradual improvement of the patient's clinical status, pyuria and renal failure persisted, necessitating institution of hemodialysis. 8 weeks after admission a renal biopsy revealed renal parenchymal malakoplakia.

Acute Kidney Injury↗
PubMed1979

Renal tubular transport of gentamicin in the rat.

The renal handling of gentamicin in the rat was examined by clearance, microinjection, and renal cortical-slice techniques. The steady-state renal clearance of 14C-gentamicin, when corrected for the 7.5% binding to plasma protein, was not significantly different from that of 3H-inulin. At the end of the renal clearance experiments, the cortical concentration of gentamicin was 93 +/- 7 microgram/g of tissue (N = 7), a concentration threefold greater than that of the medulla and 20-fold greater than that of serum. Absorption of 3H-gentamicin along the proximal convoluted tubule and loop of Henle was demonstrated by the tubular microinjection technique. No reabsorption of 3H-gentamicin was detected beyond the early distal convoluted tubule. The tubular absorption of 3H-gentamicin was load dependent. Fractional absorption of 3H-gentamicin averaged 30.1 +/- 2.7% when the dose of 3H-gentamicin injected into early proximal tubular convolutions averaged 132 +/- 17 pg. It was decreased to 13.6 +/- 2.6% when the microinjected dose of gentamicin was increased to 1996 +/- 388 pg. No evidence of transtubular absorption of 3H-gentamicin was detected during the microinjection experiments. Microperfusion of pertubular capillaries failed to demonstrate urinary precession of 3H-gentamicin over 14C-inulin, a finding which argues against a rapid transtubular secretory flux of gentamicin. Significant uptake of gentamicin was demonstrated by renal cortical slices incubated in medium containing 14C-gentamicin. The accumulation of 14C-gentamicin by renal cortical slices was not inhibited by probenecid or N1-methylnicotinamide but was inhibited by netilmicin and tobramycin. These data support the conclusion that the renal accumulation of gentamicin reflects transport of gentamicin across both the apical and basolateral membranes of proximal tubular epithelium.

Animals↗
PubMed1978

Effects of indomethacin on the vascular abnormalities of Bartter's syndrome.

We examined the hypothesis that the vascular abnormalities of Bartter's syndrome are due to excess production of prostaglandin. Balance studies and vascular reactivity studies were performed before and after indomethacin (200 mg/day) in a patient with well-documented Bartter's syndrome. During indomethacin, potassium balance became positive, serum potassium rose from 2.1--3 mEq/1 in the absence of potassium supplementation, plasma renin activity decreased from 55--3.2 ng/day and peripheral plasma PGA-like activity fell from 1460 +/- 220 to 456 +/- 71 pg/ml. Before indomethacin, forearm vasoconstrictor responses to brachial arterial infusions of angiotensin II, norepinephrine and to neurogenic reflex stimulation elicited by lower body suction were greatly depressed compared to those of normal subjects. During indomethacin these responses were restored to normal. The dose of intravenous angiotensin II required to increase diastolic blood pressure 20 mm Hg decreased from 160--30 ng/kg/min. These data support the hypothesis that the vascular insensitivity to exogenous angiotensin II, norepinephrine and to neurogenic reflex stimulation observed in this patient with Bartter's syndrome is due to excess prostaglandin. Moreover, stimulation of the renin-angiotensin-aldosterone system in this syndrome appears to be a compensatory adaptation to excess prostaglandin production.

Adult↗
PubMed1978

Evidence that the brain participates in the humoral natriuretic mechanism of blood volume expansion in the dog.

We examined the role of the central nervous system in the activation of the humoral natriuretic mechanism elicited by blood volume expansion. Studies were performed in anesthetized dogs pretreated with deoxycorticosterone acetate (15 mg/day) and sodium chloride for 12 days. An isolated dog kidney perfused with blood from the femoral artery of the volume expanded dog served as the bioassay system for the humoral natriuretic factor. In group I volume expansion of intact dogs (n = 14) with equilibrated blood promoted an increase in fractional sodium excretion (FE(Na)) from a control level of 2.6+/-0.5 to 13.6+/-1.6%, P <0.001. In the isolated kidney FE(Na) increased from 3.6+/-0.8 to 6.8+/-1.1%, P <0.01. The natriuresis from the isolated kidney occurred in the absence of significant changes in renal arterial pressure, glomerular filtration rate, plasma protein concentration, or packed cell volume, whereas renal blood flow decreased slightly. In group II (n = 20) the dogs were decapitated by means of a specially designed neck vise. In 10 dogs blood pressure was supported by a constant infusion of dopamine (3.8+/-0.7 mug/min per kg body weight). Despite the fact that in response to the same volume stimulus, decapitated dogs manifested an increase in blood volume and cardiac output similar in magnitude to that of intact dogs whereas the rise in mean arterial pressure of decapitated dogs exceeded that of intact dogs, the natriuretic response of decapitated dogs was significantly less than that of intact dogs. FE(Na) in decapitated dogs increased 4.7+/-1.1 compared to 11.1+/-1.4% in intact dogs (p <0.01). Furthermore, volume expansion of decapitated dogs failed to elicit a natriuretic response from the isolated kidney. FE(Na) in the isolated kidney measured 2.6+/-0.4 before and 2.6+/-0.4% after blood volume expansion. These data indicate that decapitation inhibits activation of the humoral natriuretic mechanism elicited by blood volume expansion and are consistent with the interpretation that the brain is the source of the natriuretic factor or that the brain participates in the activation of the humoral natriuretic mechanism at some other site in the body.

Animals↗
PubMed1977

Failure of selected endocrine organ ablation to modify the natriuresis of blood volume expansion in the dog.

1. Selected organ-ablation experiments were performed in dogs in an attempt to identify the source of the natriuretic hormone postulated to participate in the natriuresis of blood volume expansion. 2. An isolated dog kidney perfused with blood from the femoral artery of deoxycorticosterone-loaded dogs subjected to acute volume expansion with equilibrated blood served as the bioassay system for the natriuretic factor. Four groups were studied after the following procedures: group I, no ablation; group II, thyroparathyroidectomy; group III, hypophysectomy; group IV, adrenalectomy. 3. In all groups, the administration of equilibrated blood promoted a significant increase in sodium chloride excretion in the isolated kidney. The natriuresis was unrelated to changes in glomerular filtration rate, renal blood flow, renal arterial pressure, plasma protein concentration or packed cell volume. In the absence of volume expansion, sodium chloride excretion in the isolated kidney did not change or decreased. 4. These results argue against the thyroid, parathyroid, adrenal and pituitary glands as the source of natriuretic hormone.

Adrenalectomy↗
PubMed1977

Comparison of the nephrotoxicity of netilmicin and gentamicin in rats.

The nephrotoxicity of netilmicin relative to that of gentamicin was examined in Sprague-Dawley rats. Balance studies were performed on rats injected with netilmicin or gentamicin (50 mg/kg per day for 14 days, 100 mg/kg per day for 8 days, and 150 mg/kg per day for 8 days). Control rats were injected with saline. Both drugs caused a dose-related decrease in urine osmolality and increases in urine volume, water intake, and serum creatinine; however, the magnitude of these changes was significantly less in netilmicin- than in gentamicin-injected rats. Light microscopy of renal tissue revealed less proximal tubular cell necrosis in netilmicin- than in gentamicin-injected rats. There was no significant difference between the renal cortical concentrations of the two drugs. Both drugs stimulated uptake of p-aminohippurate in rat renal cortical slices to the same degree. The data indicate that netilmicin is less nephrotoxic than gentamicin in rats, that the difference in nephrotoxicity cannot be explained by a difference in drug concentration in the renal cortex, and that the ability of aminoglycosides to stimulate the organic acid transport system of proximal tubular cells does not correlate with their nephrotoxic potential.

Animals↗