Biomedical subjects

D Beauchamp

Publications and source records attributed to D Beauchamp.

At least 73 records · Page 4Linked to original sources

PubMed1992

Effect of beta-lactams on peptidoglycan metabolism of Haemophilus influenzae grown in animals.

We have examined bacterial determinants that influence beta-lactam activity in Haemophilus influenzae cells cultivated in a system that reproduces in vivo growth conditions. Bacteria grown in diffusion chambers were recovered from the peritoneal cavities of rats, and their cell properties were compared with those of bacteria grown in broth cultures by various tests performed in vitro. The rate of peptidoglycan synthesis was measured as the incorporation of [14C]alanine into cell wall material in the presence of chloramphenicol. The total incorporation of [14C]alanine into peptidoglycan was markedly increased in cells grown in rats prior to the assay but was efficiently reduced by the beta-lactams. The extent of cross-linking was lower in the peptidoglycan of in vivo-grown bacteria, as estimated by sodium dodecyl sulfate- to trichloroacetic acid-insoluble radioactive cell wall material ratios. A whole-cell labeling assay with 125I-penicillin was used to characterize the penicillin-binding proteins (PBPs). Four PBPs showed a striking reduction in the binding of the labeled penicillin in cells grown in rats. Such changes resembled the PBP alterations seen in beta-lactamase-negative clinical strains that were resistant to the beta-lactams. Although ampicillin and moxalactam showed delayed inhibitory activities in vitro for cells collected from rats, cells recovered from beta-lactam-treated rats showed evidence of antibiotic effectiveness (binding of the beta-lactams to PBPs in vivo and altered morphology), and the killing of cells exposed to antibiotics in broth or in peritoneal fluid was equally good. Finally, the frequencies of spontaneous resistance or tolerance to ampicillin or moxalactam were estimated, and there was no significant difference for in vitro- or in vivo-grown cells. These data demonstrated that the cultivation of H. influenzae in animals created changes in PBPs and the overall peptidoglycan metabolism. Such alterations did not impair the bactericidal activities of the beta-lactams, although they resulted in delayed bacterial inhibition, a phenomenon that may have important consequences in antibiotherapy.

Alanine↗

PubMed1992

Subcellular localization of tobramycin and vancomycin given alone and in combination in proximal tubular cells, determined by immunogold labeling.

The subcellular localization of tobramycin and vancomycin in the renal cortices of rats was determined with ultrathin sections by immunogold labeling. Four groups of four rats each were treated for 10 days with saline (NaCl, 0.9%), tobramycin at dosages of 20 mg/kg of body weight per 12 h intraperitoneally, vancomycin at dosages of 25 mg/kg/12 h subcutaneously, or the combination tobramycin-vancomycin. On day 11, the animals were killed, and cubes of renal cortex were fixed overnight in phosphate-buffered glutaraldehyde (0.5%), dehydrated in ethanol, and embedded in Araldite 502 resin. Ultrathin sections were made and incubated with sheep antitobramycin antibody followed by protein A-gold (15-nm diameter) complex or rabbit antivancomycin antibody followed by gold (30-nm diameter)-labeled goat anti-rabbit antibody. For the double labeling, incubations were made on opposite sides of the grid. Tobramycin was detected over the lysosomes of proximal tubular cells, but the labeling was concentrated into small areas in the matrix of the lysosomes. Vancomycin was seen over the lysosomes of proximal tubular cells and was distributed uniformly throughout the matrix of the lysosomes. In rats treated with tobramycin-vancomycin, both drugs were still detected in lysosomes of proximal tubular cells. It is concluded that tobramycin and vancomycin accumulate in lysosomes of proximal tubular cells throughout 10 days of treatment and that vancomycin has no effect on the subcellular distribution of tobramycin.

Animals↗

PubMed1992

Molecular basis of the non-beta-lactamase-mediated resistance to beta-lactam antibiotics in strains of Haemophilus influenzae isolated in Canada.

A study recently conducted across Canada showed that 64 of 2,503 clinical isolates of Haemophilus influenzae were resistant to beta-lactams without production of a beta-lactamase (L. D. Tremblay, J. L'Ecuyer, P. Provencher, M. G. Bergeron, and Canadian Study Group, Can. Med. Assoc. J. 143:895-900, 1990). The beta-lactamase-negative strains formed three distinct groups, with ampicillin MICs of 0.5 to 1, 2 to 4, and greater than or equal to 8 micrograms/ml for groups I, II, and III, respectively. We have investigated the mechanisms of resistance for eight strains originating from different infections and geographic areas. These strains were representative of groups I to III. Five strains were nontypeable, two were type B, and one was non-B. Chromosomal DNA extracted from each strain was used to transform the laboratory strain Rd. Transformants were selected on beta-lactam-containing plates and showed the same level of resistance to ampicillin as the donor strains. Differences in outer membrane proteins, porins, and lipopolysaccharide profiles on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) did not change with resistance. Functional analyses of purified porins in artificial lipid bilayer experiments did not explain resistance. Peptidoglycan synthesis was measured by incorporation of [14C]alanine into trichloroacetic acid-insoluble cell wall material in the presence of chloramphenicol. The growth rate and the rate of peptidoglycan synthesis observed for the transformants of the isogenic set did not correlate with resistance. Whole-cell labeling with 125I-penicillin revealed modifications in penicillin-binding proteins (PBPs) among the transformants. In particular, PBPs 3A and 3B (65 and 63 kDa, respectively) showed a decrease in affinity for beta-lactams in all transformants (groups I, II, and III) and correlated with an increased MIC except in the transformant of group III, which showed higher levels of resistance. Partial purification and proteolytic digestion of 125I-penicillin-labeled PBP 3B led to two types of CnBr peptide profiles on SDS-PAGE, the profiles of the transformed strains from groups I and II being different from those of the control group and group III. Finally, electron microscopy revealed a distinct cell filamentation for the group III transformants. These data clearly indicate that changes in PBPs are a common mechanism that results in a significant level of non-beta-lactamase-mediated beta-lactam resistance in H. influenzae despite serotype, origin of isolation, or geographic distribution.

Adolescent↗

PubMed1992

Modification in penicillin-binding proteins during in vivo development of genetic competence of Haemophilus influenzae is associated with a rapid change in the physiological state of cells.

By using whole-cell labeling assay with 125I-penicillin V, we observed a reduction in the binding of the radiolabeled beta-lactam to four or five penicillin-binding proteins (PBPs) in Haemophilus influenzae cells cultivated under specific conditions. PBPs 3A, 3B, 4, and 6 were altered after the growth of bacteria in diffusion chambers implanted in the peritoneal cavity of rats. PBP 2 was also modified when cells were cultivated in human cerebrospinal fluids. Because this observation may have important consequences on the efficacy of beta-lactams during antibiotic therapy, we characterized the physiological state of bacteria cultivated in animals in the hope of explaining how such important changes in cell properties develop in vivo. Since the development of natural genetic competence occurs at the stationary phase of growth in H. influenzae, we used a DNA transformation assay to evaluate the physiological state of bacteria grown in diffusion chambers implanted in rats. Chromosomal DNA isolated from an antibiotic-resistant donor strain was mixed with bacteria in diffusion chambers. At different times during a 5-h incubation period, recipient bacteria were collected from the chambers, CFU were determined by plate counting, and antibiotic-resistant transformants were isolated on selective plates. Genetic competence rapidly developed in cells grown in rats, and the frequency of transformation by test DNA was elevated. Electron microscopy revealed an irregular cell shape and blebs at the surface of bacteria cultivated in animals and in cerebrospinal fluids. In an attempt to induce a similar physiological state in vitro, we supplemented broth cultures with cyclic AMP or synchronized cultures by a nutritional upshift. No changes in PBPs were observed with supplemental cyclic AMP or during a single cell cycle. Finally, a reduction in the affinity of PBPs for 125I-penicillin V identical to that observed in bacteria grown in rats was observed in cells isolated from the stationary phase of growth in vitro. These results clearly indicate that H. influenzae cells grown in animals undergo a rapid change to a physiological state similar to that found in late-stationary-phase cultures in vitro. This observation indicates that the rational design of future and improved antibiotic therapy of H. influenzae infections should consider cell properties of slow-growing or latent bacteria.

Animals↗

PubMed1992

Epidermal growth factor accelerates renal tissue repair in a model of gentamicin nephrotoxicity in rats.

Epidermal growth factor (EGF) is a potent mitogen for renal tubular cells that possess specific high-affinity binding sites for this polypeptide. However, actual function of EGF within the kidney remains to be elucidated. We evaluated the effect of exogenous EGF administration on the rate of tubular regeneration in an experimental model of gentamicin (GT) nephrotoxicity. Female Sprague-Dawley rats were anesthetized, and a miniosmotic pump filled with mouse EGF or saline was implanted subcutaneously. Twenty-four hours later, GT (40 mg.kg-1 x 12 h-1 ip) was given for 4 and 8 days. Groups of treated animals and controls were killed either the day after cessation of treatment (days 5 and 9) or 4 and 8 days after the end of 8-day GT administration (days 12 and 16). Cortical GT levels of groups killed at days 5, 9, 12, and 16 were similar in animals infused with saline or EGF. Serum creatinine levels were significantly higher in GT-treated animals infused with EGF or saline and killed at days 9 and 12 compared with saline-treated animals infused with EGF or saline alone (P < 0.01). Blood urea nitrogen (BUN) also increased as a result of GT administration. However, in animals receiving GT and EGF and killed at day 16, mean BUN level was significantly lower (P < 0.01) compared with rats dosed with GT alone. In treated rats, the extent of tubular regeneration, evaluated by the rate of [3H]thymidine incorporation into renal cortical DNA or by the frequency of S-phase cells (histoautoradiography), was increased in a dose- and time-dependent fashion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Age-dependent gentamicin experimental nephrotoxicity.

The nephrotoxic potential of gentamicin was compared in adult (2-month-old) and old (24-month-old) female Sprague-Dawley rats in a model of short-term infusion. Animals were infused over a 12-hr period with saline or with gentamicin achieving steady-state serum levels of 56.1 +/- 11.7 (n = 18) and 59.8 +/- 14.7 (n = 17) micrograms/ml +/- S.D. (N.S.) in the adult and the old rats, respectively. Animals were sacrificed 2 hr (day 0), 4 days and 8 days after the end of the infusion. The renal cortical levels of gentamicin at day 0 (2 hr after the end of the infusion) were 1161 +/- 120 and 1125 +/- 275 micrograms/g of tissue +/- S.D. (N.S.) in the adult and the old rats, respectively. Tissue levels of gentamicin were lower in both gentamicin-treated groups on day 4 and 8 as compared with day 0 (P less than .05). The sphingomyelinase activity (measure of the lysosomal phospholipidosis) was significantly inhibited in the renal cortex of the adult and the old rats, but no significant difference was observed between these two groups. The in vivo [3H]thymidine incorporation into DNA, expressed as the percentage of the values measured in each age-matched control group, was significantly lower in the old animals as compared with that measured in the adult rats (P less than .05). No significant difference was observed in the renal function of adult rats, but a significant increase in the serum creatinine levels was measured in the old rats on day 4 of the experiment (248% of the control value, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1991

Subcellular distribution of gentamicin in proximal tubular cells, determined by immunogold labeling.

The subcellular distribution of gentamicin in rat renal proximal tubular cells was evaluated by immunogold labeling. The distribution of the drug was monitored from 10 min to 10 days following single (40 mg/kg of body weight) and multiple (5 and 20 mg/kg/12 h) injections of gentamicin. Animals were killed on day 11, and cubes of renal cortex tissue were fixed overnight in cold phosphate-buffered glutaraldehyde (0.5%), dehydrated in ethanol, and embedded in Araldite 502 epoxy resin. Ultrathin sections were made and incubated with sheep antigentamicin and then with protein A-gold (15 nm) complex. At 10 min after a single injection, the labeling was found over the brush border membrane and over the membranes of endocytic apical vesicles of proximal tubular cells. After 1 h, a similar distribution was observed and the labeling was also seen over small lysosomes located close to the brush border membrane. At 24 h, gold particles were found over large lysosomes of proximal tubular cells. Following 10 days of treatment, lysosomes of proximal tubular cells were densely labeled with gold particles. The labeling was distributed uniformly over the lysosomes, although a lower density of labeling was observed over the myeloid bodies inside the lysosomes. Necrotic proximal tubular cells showed labeling over intact lysosomes and also in the cytoplasms of the cells, in the mitochondria, and in the nucleoli. The various control experiments demonstrated the high specificity of these results. The present immunocytochemical study better documents the subcellular disposition of gentamicin in proximal tubular cells, as previously evaluated by subcellular fractionation and autoradiography. This technique will be useful for better understanding the relationship between drug disposition and drug-induced toxicity.

Animals↗

PubMed1990

Endotoxin increases the nephrotoxic potential of gentamicin and vancomycin plus gentamicin.

To assess the possible role of endotoxin as an amplification factor for experimental nephrotoxicity due to gentamicin plus vancomycin, rats were given continuous intravenous (iv) endotoxin or saline followed by twice-daily intraperitoneal (ip) saline, vancomycin (20 mg/kg ip), gentamicin (15 mg/kg subcutaneously), or both gentamicin and vancomycin. After 5 or 8 days of treatment, functional and histologic parameters of renal function were evaluated: cortical drug levels, tritiated thymidine incorporation into cellular DNA, creatinine clearance, and appearance by light and electron microscopy. In animals not given endotoxin, only rats that received gentamicin plus vancomycin developed measurable abnormalities. Endotoxin did not cause nephrotoxicity in vancomycin-treated rats. However, in endotoxin-infused rats treated with gentamicin or gentamicin plus vancomycin for 8 days, the increase in blood urea nitrogen, decrease in creatinine clearance, and rise in renal cortical DNA synthesis were more severe than those in non-endotoxin-infused rats (P less than .01). In these studies, endotoxin amplified the nephrotoxic potential of gentamicin alone and gentamicin plus vancomycin.

Animals↗

PubMed1990

Effects of daptomycin and vancomycin on tobramycin nephrotoxicity in rats.

Daptomycin is a new biosynthetic antibiotic which belongs to a new class of drugs known as lipopeptides. The objective of this study was to evaluate the effects of daptomycin and vancomycin on tobramycin-induced nephrotoxicity. Female Sprague-Dawley rats were treated during 4 and 10 days with either saline (NaCl, 0.9%) or tobramycin at doses of 4 and 40 mg/kg per day (given every 12 h [q12h] intraperitoneally). Each treatment was combined with saline, daptomycin at a dose of 20 mg/kg per day (given q12h subcutaneously), and ancomycin at a dose of 50 mg/kg per day (given q12h subcutaneously). Daptomycin and vancomycin had no effect on the intracortical accumulation of tobramycin. Daptomycin did not accumulate in renal tissue even after 10 days of treatment. Tobramycin given at a dose of 40 mg/kg per day during 10 days induced a significant inhibition of sphingomyelinase activity in the renal cortex (P less than 0.01) and increased cellular regeneration (P less than 0.01), as measured by the incorporation of [3H]thymidine into DNA of the renal cortex. These changes were minimal when daptomycin was combined with tobramycin. Histologically, signs of tobramycin toxicity were also less severe in the presence of daptomycin. The intracortical accumulation of vancomycin was not modified by tobramycin. The sphingomyelinase activity was significantly more inhibited (P less than 0.01) when vancomycin was associated with tobramycin (4 and 40 mg/kg) without affecting the rate of [3H]thymidine incorporation into DNA. Histologically, signs of tobramycin toxicity were not affected by vancomuycin, but the cellular vacuolizations which were also observed in vancomycin-treated animals were still present in the proximal tubular cells of animals that were treated with the combination vancomycin-tobramycin. This study strongly suggests that daptomycin protects animals from tobramycin-induced nephrotoxicity but that vancomycin may enhance the effect of tobramycin. We conclude that daptomycin is safe and protects kidney cells from tobramycin-induced nephrotoxicity.

Animals↗

PubMed1990

Influence of endotoxin on the intracortical accumulation kinetics of gentamicin in rats.

The mechanism by which endotoxin (lipopolysaccharide [LPS]) modifies the intrarenal distribution and the nephrotoxic potential of gentamicin is unknown. We studied the influence of LPS on the intracortical accumulation kinetics of gentamicin in rats infused intravenously for 6 h, during which time steady-state levels of the antibiotic in serum were achieved. We compared gentamicin accumulation rates (V) in normal rats and in rats receiving LPS (0.5 and 5 mg/kg) as levels in serum (S) varied from 0.5 to 130 micrograms/ml. The pharmacokinetic parameters of gentamicin were previously measured in the three groups of rats that were studied in order to reach and maintain in each rat the desired levels of antibiotic in serum during the 6 h of infusion. Two hours before the infusion of gentamicin, LPS was injected intravenously over a period of 15 min. In normal rats, the increase in S was associated with a nonlinear increase in V. The Michaelis-Menten kinetics, which was the best-fitting function, gave an apparent Vmax (maximal capacity of uptake) of 195.03 +/- 9.75 micrograms/g per h and an apparent Km (concentration in serum at Vmax/2, an index of affinity) of 34.91 +/- 4.45 micrograms/ml (linear transformation of the experimental data by the Hanes-Woolf plot: r = 0.93, n = 85). In the rats that received LPS, the increase in S was associated with a linear increase of V: for LPS at 0.5 mg/kg, V = 27.00 + 1.50 S (r = 0.94, n = 80); for LPS at 5 mg/kg, V = 22.72 + 1.48 S (r = 0.94, n = 75). We conclude that endotoxin modifies the accumulation kinetics of gentamicin in the kidney cortices of rats.

Animals↗

PubMed1990

Prolonged endotoxemia enhances the renal injuries induced by gentamicin in rats.

The aim of this study was to evaluate the role of chronic endotoxemia in the nephrotoxicity of gentamicin (GM). Saline or Escherichia coli lipopolysaccharide (LPS) was administered to conscious rats by continuous intravenous perfusion (1 mg/kg per day for 7 days) from a subcutaneously implanted osmotic pump. Twenty-four hours after surgery (day zero), treatment with saline or GM (15 mg/kg; intraperitoneally, twice a day) was started for 5 days. Levels of LPS in plasma measured by Limulus amoebocyte lysate activity decreased significantly from days 1 through 8. At days 5 and 8, the cortical concentrations of GM were higher in the LPS-perfused and GM-treated group (LPS plus GM) than they were in the saline-perfused and GM-treated group (saline plus GM) (P less than 0.05). Blood urea nitrogen and serum creatinine remained at normal levels throughout the experiment. A significant increase of cortical tubular cell regeneration was observed in the LPS plus GM animals as compared with regeneration observed in the other groups (saline plus saline, LPS plus saline, and saline plus GM), as measured by [3H]thymidine incorporation into DNA. Moreover, histopathological nephrotoxicity scores showed a synergistic toxic effect between LPS and GM. These results demonstrate that chronic perfusion of low doses of LPS potentiates the nephrotoxicity of GM.

Animals↗

PubMed1990

Effect of E. coli pyelonephritis on the intracortical accumulation kinetics of gentamicin and netilmicin in rats.

The role of serum levels on the intrarenal accumulation kinetics of gentamicin and netilmicin in normal and infected kidneys was evaluated in a short-term infusion model in conscious rats. Female Sprague-Dawley rats were infused over a period of 6 h with gentamicin and netilmicin achieving individual steady-state serum levels ranging from 0.5 to 120 micrograms/ml. The model of pyelonephritis used resulted in severe left pyelonephritis and mild right pyelonephritis. Only the right infected kidneys were studied. Gentamicin and netilmicin cortical concentrations were analysed as a function of serum levels by linear (least-squares regression analysis) and non-linear regression. For the non-linear regression analysis, the Michaelis-Menten kinetic was the best fitting curve. Steady-state elevation of serum concentrations of gentamicin and netilmicin was associated with a non-linear increase of cortical concentrations in normal kidneys, suggesting a saturable process. By contrast, in the mildly-infected right kidneys, the steady-state elevation of serum concentrations of gentamicin was associated with a linear increase of cortical concentrations while the accumulation kinetic of netilmicin showed a saturable process. At lower serum levels (therapeutic range, from 0.5 to 15 micrograms/ml) both gentamicin and netilmicin showed a first order kinetics of accumulation and netilmicin accumulated less than gentamicin in normal kidneys (p = 0.0004). By contrast, the uptake of netilmicin was higher in the right infected kidneys, as compared to the uptake of netilmicin in the normal kidneys, (p = 0.00005), and as compared to gentamicin in the respective kidneys. We conclude that renal infection modifies the intrarenal accumulation of aminoglycosides.

Animals↗

PubMed1990

Protection against gentamicin-induced early renal alterations (phospholipidosis and increased DNA synthesis) by coadministration of poly-L-aspartic acid.

Coadministration of polyaspartic acid protects against functional and pathological signs of gentamicin-induced nephrotoxicity in rats without reduction of drug accumulation in renal cortex (Williams et al., J. Pharmacol. Exp. Ther. 237: 919-925, 1986; Gilbert et al., J. Infect. Dis. 159: 945-953, 1989). We have assessed the influence of polyaspartic acid on the early alterations induced in kidney cortex by gentamicin, namely the lysosomal phospholipidosis and the increase in cell turnover. We used an infused rat model in which animals received a total dose of 100 mg/kg of gentamicin over 12 hr. Renal cortex was examined 2 hr (day 0) and 48 hr (day 2) after treatment. All animals received an injection of [3H]thymidine (200 microCi i.p.) before sacrifice. Coadministration of polyaspartic acid (drug-polypeptide mass ratio 1:2.5) did not modify the drug serum levels, as recorded during or shortly after the infusion. Yet, it was associated with 1) an increased (approximately 35%) drug cortical content at day 0; 2) a significant protection against both biochemical (decrease of sphingomyelinase activity at day 0; increase of lipid phosphorus content at day 2) and morphological (enlargement of lysosomes and deposition of myeloid bodies at day 2) signs of lysosomal phospholipidosis in proximal tubular cells; and 3) an almost complete protection against increased cell turnover (mostly in proximal tubules) in cortex at day 2, as assessed by the measurement of [3H]thymidine incorporation into DNA and the enumeration of S-phase cells after histoautoradiography. In addition, morphological studies revealed a larger number of apical vacuoles in proximal tubular cells of animals receiving polyaspartic acid alone (but not in combination with gentamicin), and the deposition of osmiophilic, homogenous material in the lysosomes of animals receiving the combination of gentamicin and polyaspartic acid. Together with the results reported in two companion papers (Kishore et al., J. Pharmacol. Exp. Ther. 867-874, and 875-885, 1990), these results provide evidence that protection afforded by polyaspartic acid extends to the earliest cellular alterations described in kidney for gentamicin, namely the lysosomal phospholipidosis, suggesting that this protecting agent exerts blocking effect from this step in the cascade of events relating drug cortical accumulation to renal toxicity.

Animals↗

PubMed1989

Effect of age on the intracortical accumulation kinetics of gentamicin in rats.

We have evaluated the influence of age on the intracortical accumulation kinetics of gentamicin in conscious male rats by using a short-term infusion model. Animals were infused with gentamicin over a 6-h period and achieved individual steady-state levels in serum ranging from 0.5 to 12 micrograms/ml. Young rats were about 3 months old, and old rats were about 6 months old. The steady-state elevation of concentrations of gentamicin in serum was associated with a linear increase of the cortical concentrations in both groups. However, the accumulation of gentamicin was lower in the renal cortex of the old rats than in the renal cortex of the young rats. We conclude that the intrarenal uptake of gentamicin is modified during aging. Further studies must be undertaken to better understand the role of age on the mechanism of uptake and the toxicity of aminoglycosides.

Aging↗

PubMed1989

Influence of indomethacin on the intrarenal uptake of gentamicin in endotoxemic rats.

Gentamicin is a commonly used antibiotic for the treatment of gram-negative-bacterial infections. Bacterial endotoxin is liberated during antibiotic therapy, and we have shown that endotoxemic animals accumulate more aminoglycosides in their renal parenchyma than normal animals. Vasoactive mediators, such as prostaglandins and thromboxanes, are released after endotoxin and are involved in inflammation. Indomethacin, a nonsteroidal anti-inflammatory drug known to inhibit the synthesis of these hormones, was infused intravenously as a bolus (3.0 mg/kg) or as a bolus followed by a continuous infusion (0.75 mg/kg per h) to rats given gentamicin. Levels of gentamicin in serum and kidney were increased 2 h post-antibiotic treatment in the endotoxemic animals. Renal function was not significantly disturbed. Indomethacin given as a bolus failed to correct the disturbed intrarenal pharmacokinetics of gentamicin induced by endotoxin. However, a bolus followed by continuous infusion of indomethacin resulted in low cortical and high papillary levels of antibiotic. These changes were correlated with the inhibition of prostaglandin synthesis from the kidney. These observations suggest an important role for prostaglandins in the interaction among endotoxin, aminoglycosides, and the kidney. Specific inhibitors of arachidonic acid metabolites should be investigated to further understand the mechanisms of this interaction.

Alprostadil↗

PubMed1989

Intrarenal distribution of vancomycin in endotoxemic rats.

We previously observed that the intrarenal distribution of aminoglycosides was modified by Escherichia coli endotoxin in the absence of any major renal physiological disturbance or histological changes. In the present study, we evaluated the role of E. coli endotoxin on the intrarenal distribution of vancomycin. At the beginning of the experiment, female Sprague-Dawley rats were infused intravenously with saline (control) or endotoxin (0.25 mg/kg) during 15 min. Thereafter, saline was constantly infused for the following 4 h. Two hours after the beginning of the infusion, animals were injected intravenously with a single dose of vancomycin (20 mg/kg). The drug levels in serum; renal cortex, medulla, and papilla; and urine were evaluated from 0.08 to 24 h after injection. Analysis of the area under the curve of the drug concentration in the different kidney components versus time showed a higher accumulation of vancomycin in the renal cortex and medulla in the endotoxin-infused rats than in the normal rats (P less than 0.01). Endotoxin was associated with an increase in the half-life in serum (P less than 0.01) and a lower elimination rate constant. The total clearance of vancomycin from plasma was significantly decreased in endotoxin-treated rats (P less than 0.01). These results demonstrate that endotoxin modifies the renal handling of vancomycin.

Animals↗

PubMed1988

Influence of hydrocortisone on gentamicin-induced nephrotoxicity in rats.

Many risk factors associated with aminoglycoside nephrotoxicity have been identified in humans and experimental animals. They include an initial high rate of creatinine clearance, high initial peak levels in serum, age, sex, duration of therapy, liver disease, and renal infection. The concomitant administration of steroids has never been investigated. We evaluated the role of hydrocortisone on gentamicin-induced nephroxicity in a model of infused rats. We showed that hydrocortisone given over 3 days after the infusion did not modify the gentamicin half-life in the renal cortex, gentamicin-induced lysosomal phospholipidosis, or histopathology but did reduce significantly the 3H/DNA ratio on day 4 after gentamicin infusion. We concluded that hydrocortisone interferes with the postnecrotic cellular regeneration process, an important step that is responsible for the recovery of normal kidney structure following toxic injuries associated with aminoglycoside therapy.

Animals↗

PubMed1987

Influence of hydrocortisone succinate on intrarenal accumulation of gentamicin in endotoxemic rats.

Gentamicin is a commonly used antibiotic in the treatment of gram-negative infections including septicemia and pyelonephritis. Bacterial endotoxin is liberated during antibiotic therapy and may lead to endotoxemic shock. Steroids such as hydrocortisone are generally recommended in the treatment of endotoxemic shock. There are very limited data on the influence of endotoxin or corticosteroids on the pharmacology of antibiotics, especially aminoglycosides, which are nephrotoxic. We studied the influence of both Escherichia coli endotoxin and hydrocortisone succinate on the renal uptake of gentamicin in rats. Animals were injected intravenously with endotoxin (0.25 mg/kg) and/or hydrocortisone (25 mg/kg) plus gentamicin (10 mg/kg). Gentamicin levels in the serum and renal parenchyma as well as renal function and histology were evaluated. Both endotoxin and hydrocortisone given alone increased the concentration of gentamicin in the renal cortex (P less than 0.05). Normal values in serum were observed in all groups at most time intervals. When administered together, endotoxin and hydrocortisone did not potentiate each other. The combination of endotoxin and hydrocortisone gave significantly higher levels of gentamicin than endotoxin or hydrocortisone alone when endotoxin was injected 3 h before hydrocortisone (P less than 0.05). Blood pressure and cardiac frequency were normal when gentamicin was given. Endotoxin alone slightly decreased the glomerular filtration rate, and hydrocortisone alone slightly modified renal plasma flow. The combination of both drugs did not significantly affect renal function. No histological lesion was noted on light microscopy in animals receiving endotoxin. Competitive or synergistic activity of endotoxin, gentamicin, and hydrocortisone at the cellular level, especially on membranes or lysosomes, might explain in part our observation on the renal uptake of gentamicin. By increasing the total amount of drug within the kidney, endotoxin and hydrocortisone might increase the risk of nephrotoxicity associated with aminoglycosides.

Animals↗