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Acetaminophen (APAP)-induced nephrotoxicity is age dependent in male Sprague-Dawley rats: nephrotoxicity occurs at lower dosages of APAP in 12- to 14-month olds compared with 2- to 3-month olds. The mechanisms responsible for enhanced nephrotoxicity in 12-month-old Sprague-Dawley rats are not entirely clear, but may be related to age-dependent differences in APAP metabolism in liver and/or kidney. Major pathways of hepatic APAP metabolism include sulfation and glucuronidation; glutathione conjugation represents a pathway for detoxification of reactive oxidative APAP metabolites. The present studies were designed to quantify in vitro activity of three Phase II enzyme activities: glutathione S-transferase using 1-chloro-2,4-dinitrobenzene as substrate, UDP-glucuronyl transferase using APAP as substrate, and sulfotransferase using APAP as substrate, in subcellular fractions of liver and kidney of 3-, 12-, 18-, and 30-month-old naive male Sprague-Dawley rats. In liver, glutathione S-transferase, UDP glucuronyl transferase, and sulfotransferase activities were not significantly different in rats from 3 through 30 months of age. Renal UDP glucuronyl transferase and sulfotransferase activities were similar in rats from 3 through 30 months of age. In contrast, renal glutathione S-transferase activity was characterized by a lower Km in 12- and 30-month olds when compared with 3-month olds. These data suggest that the reduced total systemic clearance of APAP in 12-month-old male Sprague-Dawley rats previously observed cannot be attributed to age-dependent differences in hepatic APAP metabolism. In addition, it is unlikely that differences in renal APAP metabolism contribute to age-dependent APAP nephrotoxicity.

Acetaminophen (APAP)-induced nephrotoxicity is age-dependent in male Sprague-Dawley (SD) rats: middle-aged (9-12 months old) rats exhibit nephrotoxicity at lower dosages of APAP than do young adults (2-3 months old). The present study was designed to test the hypothesis that the intrinsic susceptibility of renal tissue to APAP toxicity is increased in middle-aged rats. APAP toxicity was evaluated in renal slices from naive 3- and 12-month-old male SD rats incubated with 0-50 mM APAP for 2-8 h. Renal slice glutathione (GSH) and APAP concentrations were determined; renal function was assessed by organic anion (para-aminohippurate, PAH) and cation (tetraethylammonium, TEA) accumulation; and cell viability was assessed by lactate dehydrogenase (LDH) leakage. At each concentration of APAP tested, accumulation of APAP by renal slices was similar in 3- and 12-month-olds. APAP toxicity in renal slices from both 3- and 12-month-old rats was characterized by concentration-dependent increases in LDH leakage. In contrast to APAP nephrotoxicity in vivo, APAP toxicity in renal slices was accompanied by decreased accumulation of PAH and TEA. Additionally, APAP produced marked reductions in renal slice GSH content in a concentration-dependent manner: however, in contrast to APAP nephrotoxicity in vivo, APAP-induced GSH depletion in vitro did not precede cytotoxicity. No consistent age-dependent differences in the time- and concentration-response curves for APAP nephrotoxicity were observed. These data suggest that APAP cytotoxicity in vitro is not increased in 12-month-old rats. However, since the pattern (and mechanisms) of APAP cytotoxicity in vitro appears to be different from that observed in vivo, extrapolation of in vitro cytotoxicity to in vivo nephrotoxicity is limited. Therefore, age differences in intrinsic susceptibility of the intact kidney cannot be excluded as a mechanism contributing to enhanced APAP nephrotoxicity in middle-aged rats.

Protein degradation in the kidney occurs mainly in lysosomes, organelles which may also accumulate nephrotoxic chemicals. The goal of this study was to evaluate the effects of intracellular accumulation of gentamicin, cephaloridine and cisplatin on lysosomal digestion of the protein lysozyme. Gentamicin (15 or 30 mg/kg/day for 3 or 5 days), cisplatin (2.5 or 5 mg/kg) or cephaloridine (500, 1000, 2000 or 2500 mg/kg) was administered ip to male Wistar rats. The main site of the nephrotoxic effects of these compounds was the proximal tubule where these agents differentially affected S1, S2 and/or S3 segments. A 2- and 4-fold increase of the excretion of N-acetyl-beta-D-glucosaminidase (NAG) was observed in the urine from cisplatin- and gentamicin-treated rats, respectively; no change in enzyme excretion occurred after cephaloradine. One hour prior to sacrifice, rat were given 0.3 mg of unlabelled lysozyme in combination with 125I-lysozyme in 0.3 mL saline. Renal cortical slices were prepared and incubated for 15, 30, 60 and 90 min. Release of trichloroacetic acid (TCA) soluble radioactivity into the medium was assumed to quantify lysosomal degradation of lysozyme. Accumulation of p-amino-hippurate (PAH) in renal cortical slices and changes in blood urea nitrogen (BUN) concentration were used as indices of renal damage. TCA-soluble radioactivity increased in the medium from kidney slices from control rats to 50% of the total radioactivity after 90 min incubation. In gentamicin-treated rats, lysozyme degradation was significantly decreased by doses of 15 and 30 mg/kg/day after 3 and 5 days of exposure in the absence of any changes in BUN or PAH accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Preincubation of renal cortical slices with chloroform (CHCl3) from male, but not female, mice resulted in a subsequent decrease of the ability of the slices to accumulate the organic ions, p-aminohippurate (PAH) and tetraethylammonium (TEA). These sex-related differences, the time required for manifestation of this effect (60 to 90 min), and the concentration dependency (0 to 50 mumol, 0 to 4 microliter CHCl3) were similar to in vivo observations on CHCl3 nephrotoxicity in mice. Furthermore, an equimolar concentration of deuterated CHCl3 (CDCl3) in vitro was less effective than CHCl3 in decreasing PAH and TEA accumulation in male renal cortical slices. The effects of CHCl3 on PAH and TEA accumulation could be diminished or blocked by preincubation with CHCl3 in the presence of carbon monoxide or at 0 degrees C, respectively. The nephrotoxicity of CHCl3 in vitro was increased in renal cortical slices from male mice pretreated with diethyl maleate. Thus, this in vitro model with mouse renal cortical slices and the sex-related differences in CHCl3 nephrotoxicity suggests that the kidney may metabolize CHCl3 in situ to a nephrotoxic metabolite.

Various ketonic agents potentiate the hepatic and renal toxicity of halogenated solvents in mice and rats. Characteristics of CHCl3 nephrotoxicity and of 2-hexanone potentiation were evaluated in adult male Fischer 344 rats pretreated with vehicle (oil, 10 ml/kg, po) or 2-hexanone (10 mmol/kg, po) 18 hr prior to CHCl3 exposure. In contrast to the liver, little metabolism of 14CHCl3 by renal cortical microsomes from vehicle- or 2-hexanone-pretreated rats was detected. However, CHCl3 produced a concentration-related dysfunction when added to renal cortical slices from Fischer 344 or Sprague-Dawley rats. The degree of CHCl3 toxicity in vitro was not altered when renal cortical slices were preincubated with CHCl3 (8.5 microliter) under an atmosphere of carbon monoxide. In renal cortical slices, deuterated-CHCl3 was less toxic than CHCl3. Although 2-hexanone pretreatment increased renal slice metabolism of 14CHCl3 twofold, this increase was not associated with an increase in nephrotoxicity after direct exposure of slices to CHCl3 (0 to 10 microliter) in vitro. CHCl3 (0.5 ml/kg, ip) did not alter renal cortical glutathione concentrations in vehicle or 2-hexanone pretreated rats. The association of 14CHCl3-derived radiolabel was increased over control by 2-hexanone pretreatment in protein, lipid, and acid soluble fractions from the renal cortex by approximately two-, two-, and fivefold, respectively. In conclusion, renal cytochrome P-450 did not appear to mediate CHCl3 metabolism and nephrotoxicity in the rat to the extent observed previously in mice. 2-Hexanone appeared to potentiate nephrotoxicity by a mechanism different than that observed in rat liver.

This study was undertaken to investigate the effects of pre- and/or postnatal maternal protein deprivation (PD) on renal functional development in the offspring. Pregnant rats were fed either a control (24% protein) or low (8 or 10%) protein diet during gestation and lactation. Progeny of these dams were cross-fostered at birth, yielding four experimental groups: pups born of control dams and nursed by PD or control dams and pups born of PD dams and nursed by control or PD dams. While the effects of prenatal PD on body and kidney growth were negligible, PD during the nursing period appeared to have a more profound effect on body and kidney weight. Renal transport functions, quantified in vitro, were differentially affected by these dietary manipulations. Renal transport capacity for organic acids and bases was depressed in pups nursed by PD dams. Maturation of the renal organic acid transport system was also delayed in these pups. alpha-Aminoisobutyric acid accumulation by renal cortical slices was enhanced only in 10-day old rats stressed by pre- and postnatal maternal PD. Renal gluconeogenic and ammoniagenic capacity was not impaired by these dietary manipulations. No differences in protein or water content of renal cortical slices were observed.

The effect of tolmetin on prostaglandin synthesis by minces of rat renal medulla and on prostaglandin cyclooxygenase of rabbit renal medulla was determined in vitro. The effect of tolmetin was compared to the effects of indomethacin and ibuprofen. Pretreatment of rats in vivo with tolmetin, indmethacin or ibuprofen reduced prostaglandin synthesis by minces of renal medulla. Incubation of medullary tissue in medium containing tolmetin or indomethacin also decreased prostaglandin production. Both drugs reduced O2 consumption by prostaglandin cyclooxygenase from rabbit renal medulla. In addition, the effect of tolmetin, indomethacin and ibuprofen on renal blood flow and the intrarenal distribution of renal blood flow was measured in anesthetized dogs. Tolmetin and ibuprofen resemble indomethacin in reducing renal blood flow and in shifting the distribution of renal cortical flow from the inner cortex toward the outer cortex. It is concluded that tolmetin is an effective inhibitor of prostaglandin synthesis and affects renal function in a fashion similar to other prostaglandin synthesis inhibitors.

Strain differences in susceptibility of rats to acetaminophen (APAP)-induced nephrotoxicity have been reported previously. Young adult male Fischer 344 (F344) rats are susceptible, whereas weight-matched Sprague-Dawley (SD) rats are not susceptible to APAP nephrotoxicity. Susceptibility to APAP nephrotoxicity is also age dependent, at least in F344 rats. Middle-aged (12-15 months old) male F344 rats are more susceptible to APAP-induced nephrotoxicity than are young adult (2-4 months old) males. APAP nephrotoxicity in aging SD rats has not been evaluated. The present studies were designed to define strain differences in the nephrotoxicity of APAP and p-aminophenol (PAP), a nephrotoxic metabolite of APAP, using 2-, 3-, and 9- to 12-month-old F344 and SD rats. At 2 months of age, F344, but not SD, rats were susceptible to APAP-induced nephrotoxicity. However, at 3 months of age, strain differences were less marked, as susceptibility to APAP nephrotoxicity appeared to increase between 2 and 3 months of age only in SD rats. By 9-12 months of age, susceptibility to APAP nephrotoxicity was comparable in F344 and SD rats. No age- or strain-related differences were observed in the excretory pattern of urinary APAP and metabolites that might explain the increased susceptibility of aging rats to APAP nephrotoxicity. Strain differences in age-matched rats were not marked for PAP-induced nephrotoxicity. Susceptibility of both 3- and 12-month-old F344 and SD rats to PAP-induced nephrotoxicity was greater compared to strain-matched 2-month-old rats. In both F344 and SD rats, PAP nephrotoxicity increased only modestly between 3 and 12 months of age, indicating that increased susceptibility to PAP probably does not play a major role in the age-dependent increase in APAP nephrotoxicity. Thus, strain differences in APAP nephrotoxicity decrease with advancing age. The mechanisms mediating the increased susceptibility to APAP nephrotoxicity in middle-aged rats are not known but may relate, at least in part, to age-dependent differences in pharmacokinetics. The present study highlights the importance of considering the age of rats when evaluating drug toxicity. Even in young adult rats, subtle maturational changes in drug metabolism and/or disposition may occur, making toxicological evaluation in weight-matched rats of different strains and ages inappropriate.

Middle-aged male Sprague-Dawley (SD) rats (9-12 months) are more susceptible to acetaminophen (APAP)-induced nephrotoxicity than are young (2-3 months) adult males. The present studies were designed to evaluate the role of pharmacokinetics and renal and hepatic metabolism of APAP in age-dependent nephrotoxicity. Following 750 mg/kg APAP, ip, a nephrotoxic dosage in 12-month-old but not 3-month-old rats, renal cortical APAP concentrations were significantly greater in 12-month-old compared with 3-month-old SD rats at 3, 4, and 6 hr after treatment. Renal medullary APAP concentrations in 12 month-old rats were significantly greater than in 3-month-old rats at 2, 3, and 5 hr after treatment. Serum APAP concentrations were significantly elevated in 12-month-old compared with 3-month-old rats from 2 through 5 hr after APAP (750 mg/kg ip). However, APAP tissue/serum concentration ratios were similar in 3- and 12-month-old rats, indicating that differences in tissue concentration were secondary to increased serum concentrations in older rats. Conjugated APAP metabolites in blood were similar in 3- and 12-month-olds during the initial 2-3 hr after 750 mg/kg APAP, ip, but began to accumulate in 12-month-old but not 3-month-old rats within 6-8 hr after APAP administration, perhaps secondary to declining renal function. After 500 mg/kg APAP, iv, blood APAP concentrations were markedly elevated in 12-month-old compared with 3-month-old rats during the entire course of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

In mice, only males are susceptible to chloroform (CHCl3) nephrotoxicity and the susceptibility appears to be related to renal mixed function oxidase activity. There were sex-related differences of renal cytochrome P-450 and b5 concentrations and of ethoxycoumarin O-deethylase activity in mouse kidneys; in all cases activity was higher in males. Castration of male mice eliminated susceptibility to CHCl3 nephrotoxicity and reduced renal mixed function oxidases to concentrations observed in female mice. Treatment of male and female mice with testosterone increased the susceptibility to CHCl3 nephrotoxicity and increased renal mixed function oxidases to similar activities in both sexes. Previous data have suggested that CHCl3 is metabolized in situ by the kidney, possibly by a mechanism similar to that occurring in the liver. The data from this investigation are consistent with the concept that CHCl3 is metabolized by a cytochrome P-450-dependent mechanism in the kidney.

These experiments were designed to demonstrate that pretreatment of newborn dogs with penicillin will enhance maturation of the renal organic anion transport system in vivo. Littermate pups were injected with procaine penicillin G (300,000 I.U./kg b.i.d. for 3 days) or saline before 2 weeks of age. Animals were surgically prepared on day 16 or 17. Transport of p-aminhippurate (PAH), as an indicator of renal organic anion transport, was quantified by the following procedures: 1) disappearance of a bolus injection from the plasma, 2) renal extraction and 3) rate of secretion in steady-state clearance experiments. The renal handling of insulin was measured simultaneously in all procedures for comparison. Penicillin-treated animals excreted a single intravenous bolus of PAH more rapidly than control animals, with the T1/2 decreased and the constant of elimination (Ke) increased. The extraction of PAH by kidneys of penicillin-treated animals was 165% that of controls. Similarly, the tubular secretion of PAH was increased in treated pups. These data confirm that in newborn animals the renal handling of organic anions in vivo is enhanced by pretreatment with a substrate of the secretory system.

Renal and hepatic microsomal enzyme activities were measured in ICR male mice treated with phenobarbital (PB), 3-methylcholanthrene (3MC), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or polychlorinated biphenyls (PCB). The effect of these agents on subsequently administered single doses of chloroform (CHCI3) were also determined. 3MC, TCDD and PCB increased renal as well as hepatic microsomal enzyme activities. PB increased hepatic but not renal microsomal enzyme activities. The hepatotoxicity of CHCI3 was increased by pretreatment with PB but decreased by pretreatment with TCDD. 3MC and PCB were without effect on CHCI3-induced liver damage. Pretreatment with 3MC, TCDD or PCB reduced the renal toxicity of CHCI3, but PB had no effect on CHCI3-induced kidney damage. Since at least one product of enzymatic metabolism of CHCI3 is believed to be a toxic, reactive intermediate the differential effects of inducers of microsomal drug-metabolizing enzyme activities on the renal and hepatic toxicities of CHCI3 strongly suggest that the CHCI3 metabolite(s) ultimately responsible for renal and hepatic damage are not generated at a common site. That is the metabolite responsible for hepatic is probably generated in the liver and the metabolite responsible for renal damage is probably generated in the kidney.

The effects of renal development on the response of newborns to acetazolamide were determined in an animal model, 5- and 20-day-old piglets. Increasing doses of acetazolamide increased both sodium and potassium excretion in 5-day-old piglets. Sodium excretion increased from 1.89 muEq/min during control periods to 15.7 muEq/min during infusion of acetazolamide (75 mg/kg/h). Potassium excretion increased to 20 muEq/min during acetazolamide infusion and urine pH increased from 5.7 to over 8.0. Sodium excretion by 20-day-old piglets given acetazolamide was similar to that of 5-day-old piglets but potassium excretion was twice as great (40 muEq/min). Changes in urine pH of the two groups were identical. It is concluded that the natriuretic response of 5-day-old piglets to acetazolamide is similar to that of older animals. In newborn piglets, moderate increases in sodium excretion by acetazolamide were accompanied by a marked kaliuresis. These data may identify a role for carbonic anhydrase in potassium excretion by newborn similar to that of adults.

The realtionship between in vitro prostaglandin production by renal medullary tissue and hypertension was investigated in three models of hypertensive rat, i.e., DOCA, Goldblatt and SHR. Medullary minces were incubated for 30 minutes. Following incubation tissue PGE2 concentration was quantified using mass fragmentography. Media PGE2 concentrations were quantified using radioimmunoassay. Concentrations of PGE2 in tissue from Goldblatts and SHRs were significantly less than normotensive controls. The concentration of PGE2 in media after incubating SHR tissue was significantly less than normotensives. The data suggest that alterations in PGE2 metabolism are similar in Goldblatt and SHR hypertension.

Cephaloridine produces renal cortical injury, but the precise mechanism responsible for this nephrotoxicity remains unclear. Recently cephaloridine has been shown to deplete reduced glutathione (GSH) concentration selectively in renal cortex. Cephaloridine nephrotoxicity can be potentiated by diethyl maleate (a GSH depletor), but no glutathione conjugate can be detected. Thus, it was of interest to investigate further the mechanism of depletion of renal cortical GSH by cephaloridine. In the present study, cephaloridine markedly decreased GSH in rat and rabbit renal cortex while concomitantly increasing oxidized glutathione (GSSG). Furthermore, cephaloridine increased lipid peroxidation specifically in renal cortical cells. Conjugated diene formation (an index of lipid peroxidation) was increased in renal cortex but not in the liver shortly following administration of cephaloridine. Removal of selenium and/or vitamin E from the diet, which should enhance lipid peroxidation, potentiated cephaloridine nephrotoxicity and enhanced cephaloridine-induced morphological damage in the kidney. These findings are consistent with a major role of lipid peroxidation in the etiology of cephaloridine nephrotoxicity.

Metabolism of chloroform (CHCl3) by a cytochrome P-450-dependent process to a reactive metabolite may be required to elicit hepatic and renal toxicities. Specific inducers or inhibitors of cytochrome P-450 have been employed frequently as tools to demonstrate this relationship between metabolism and toxicity in the liver. The experiments reported herein were designed to identify the relationship between metabolism and toxicity of CHCl3 in the kidney of rabbits, a species in which renal cytochrome P-450 is induced by phenobarbital. Pretreatment with phenobarbital enhanced the toxic response of renal cortical slices to CHCl3 in vitro as indicated by decreased p-aminohippurate and tetraethylammonium accumulation. Phenobarbital pretreatment also potentiated in vitro 14CHCl3 metabolism to 14CO2 and covalently bound radioactivity in rabbit renal cortical slices and microsomes. Addition of L-cysteine significantly reduced covalent binding in renal microsomes from both phenobarbital-treated and control rabbits and was associated with the formation of the radioactive phosgene-cysteine conjugate 2-oxothiazolidine-4-carboxylic acid (OTZ). Formation of OTZ was enhanced in renal microsomes from phenobarbital-pretreated rabbits. Thus, this in vitro model supports the hypothesis that the kidney metabolizes CHCl3 to the nephrotoxic metabolite, phosgene.

Effects of age and sex on hexachloro-1,3-butadiene (HCBD) nephrotoxicity were determined 24 hours after a single dose (0, 25, 50, 100 or 200 mg/kg) in 28- and 63-day-old Fischer 344 rats. HCBD treatment significantly increased the kidney to body weight ratio but had little effect on the liver to body weight ratio. The 28-day-old rats were more susceptible to HCBD nephrotoxicity judged by elevated blood urea nitrogen, decreased renal cortical accumulation of p-aminohippurate and tetraethylammonium. Adult female rats (63-day-old) appeared to be more susceptible to HCBD nephrotoxicity than males at the low dose (50 mg/kg).

Daily subcutaneous administration of 20 or 100 mg/kg gentamicin for 4 days significantly decreased pyridoxal-5'-phosphate and lysosomal specific phosphatidylinositol-phospholipase C (PI-PLC) in newborn rat kidney. The fall in PI-PLC was associated with an elevation in renal phosphatidylinositol, phosphatidylserine, and phosphatidylcholine. The 100 mg/kg gentamicin dose also produced a rise in renal sphingomyelin, phosphatidylethanolamine, phosphatidylglycerol, and total phospholipid (TPL) accompanied by inhibition in the activities of Na+,K+-ATPase and alkaline phosphatase. In contrast, daily intraperitoneal injection of 100 mg/kg vancomycin for 4 days failed to markedly alter renal metabolic parameters. However, the 500 mg/kg vancomycin dose increased kidney weight, TPL, and all individual phospholipid class concentrations accompanied by inhibition of lysosomal specific PI-PLC activity and reduced pyridoxal-5'-phosphate levels. Simultaneous administration of 20 mg/kg gentamicin with either vancomycin dose resulted in renal alterations similar to those produced by gentamicin alone. Concurrent treatment with 100 mg/kg aminoglycoside and either vancomycin dose produced changes in kidney which were similar to those produced by gentamicin alone, except for a synergistic rise in PI as well as a greater fall in alkaline phosphatase and pyridoxal-5'-phosphate. Surprisingly, the concentration of gentamicin and vancomycin was less in newborn kidneys of rats receiving a simultaneous high dose of vancomycin and aminoglycoside treatment compared to levels found in animals given either antibiotic separately. The lack of potentiation of nephrotoxicity in newborns administered a combination of vancomycin and gentamicin may be due to decreased accumulation of either antibiotic in kidney.

Rats and mice were pretreated with beta-naphthoflavone (BNF) at 100 mg/kg/day, ip, for 4 days, or polybrominated biphenyl (PBB) as a single ip dose at 150 mg/kg, and the temporal changes in renal mixed function oxidase (MFO) activity and ultrastructural changes in the proximal tubule were examined. Rat renal cytochrome P-450 (P-450), ethoxycoumarin-O-deethylase (ECOD), and ethoxyresorufin-O-deethylase (EROD) were increased 5 days following the first dose of inducer. P-450 content and enzyme activity peaked on Day 5 to Day 10 and returned to control values by Day 15. BNF and PBB caused proliferation of smooth endoplasmic reticulum (SER) in only the S3 segment of the rat proximal tubule. Histologic analysis indicated that there was a close correlation between the temporal changes in renal MFO activity and proliferation of SER in the S3 segment of the proximal tubule. In contrast to the rat, mouse renal P-450 and ECOD were not induced by either BNF or PBB nor was there any significant proliferation of SER in any segment of the proximal tubule. Mouse renal EROD was slightly increased on Day 5 but not Day 10 or 15 by BNF; PBB had no effect. In addition to proliferation of SER, these inducers also caused proliferation of peroxisomes in the rat and mouse proximal tubule. These results demonstrate a temporal relationship between induction of rat renal MFOs and proliferation of SER in specific sections of the proximal tubule and thus suggest that induction of these renal enzymes may also be restricted to specific cell populations of the kidney. A species difference apparently exists since proliferation of SER was not observed in the mouse.

In this investigation, we have attempted to determine whether chloroform (CHCl3)-induced nephrotoxicity might be due to its metabolism to phosgene (COCl2) in the kidney. We have found that kidney homogenates from DBA/2J male mice in the presence of glutathione metabolize CHCl3 to 2-oxothiazolidine-4-carboxylic acid (OTZ). This product appears to be formed by the initial trapping of COCl2 by two molecules of GSH to form diglutathionyl dithiocarbonate (GSCOSG). Kidney gamma-glutamyl transpeptidase can rapidly metabolize GSCOSG to N-(2-oxothiazolidine-4-carbonyl)-glycine which is then hydrolyzed, possibly by cysteinyl glycinase to OTZ. The finding that deuterium-labeled chloroform (CDCl3) was less nephrotoxic and depleted less renal GSH than did CHCl3 suggests that the metabolism of CHCl3 to COCl2 may also occur in the kidney in vivo and lead to nephrotoxicity.

In utero exposure of rats to methylmercury has been reported to produce degenerative and hyperplastic changes in renal proximal and distal tubules, although no assessment of postnatal renal functional capacity was made. CH3HgCl was administered ip to Sprague-Dawley rats on Day 8 of gestation at 4 or 6 mg Hg/kg or on Days 8, 10, and 12 at 4 mg Hg/kg (3 x 4 mg Hg/kg). These doses produced no overt toxicological effects nor had any effect on litter size, body weight, or kidney weight to body weight ratios. The concentration of mercury in kidneys, liver, and brain at 1 and 7 days postpartum was dose-related but was not detectable at 42 days. In vitro renal function was assessed in renal cortical slices from rats at 1, 7, and 42 days postpartum by determining the ability to accumulate organic ions and to generate glucose. Additionally, parameters of in vivo renal function were determined in normopenic, hydropenic (5 pressor units/kg ADH, sc, 18 hr water deprived), and in volume-loaded male rats at 42 days postpartum. At 42 days postpartum in the 3 x 4 mg Hg/kg treatment group, p-aminohippurate accumulation was depressed slightly as was the ability to eliminate Na+ and water in volume-loaded rats. These data suggest that postnatal renal physiological sequelae to prenatal administration of methylmercury may be less than predicted from histological studies.

Renal xenobiotic metabolism can result in production of electrophiles or free radicals that may covalently bind macromolecules or initiate lipid peroxidation. The mechanisms of renal xenobiotic metabolism may vary in different anatomical regions. Kidney cortex contains a cytochrome P-450 system while medulla contains a prostaglandin endoperoxidase. Recently cysteine conjugated-lyase has been implicated in production of reactive intermediates. Metabolic activation may be amplified by accumulation of xenobiotics within renal cells due to tubular concentrating and/or secretory mechanisms. Additionally, renal xenobiotic detoxicification can occur by conjugation with glucuronide, sulfate or glutathione.

Female Fischer 344 rats administered p-nitrophenol (0.05 mmol/kg) excrete more p-nitrophenylglucuronide in the urine than males (35.9 +/- 2.9 vs. 14.1 +/- 4.0% of total urinary metabolites, respectively). In contrast, hepatic microsomes prepared from male rats have higher UDP-glucuronyltransferase activity toward p-nitrophenol than hepatic microsomes from females (6.49 +/- 0.67 vs. 3.20 +/- 0.17 nmol/min/mg of protein, respectively). Sex differences in p-nitrophenylglucuronide excretion may be due to sex differences in either biliary excretion of glucuronide conjugate or in extrahepatic conjugation of p-nitrophenol. UDP-glucuronyl-transferase activity in renal microsomes prepared from male and female rats toward p-nitrophenol was 0.21 +/- 0.09 nmol/min/mg of protein and 0.91 +/- 0.02 nmol/min/mg of protein, respectively. Vmax was greater in females than in males; Km was not sex linked. Similar in vitro sex differences were also observed with 1-naphthol as the aglycone. In contrast, renal microsomes prepared from male or female rats did not glucuronidate morphine. Likewise, no sex differences in the excretion of morphine glucuronide were observed (16.4 +/- 4.8 vs. 23.9 +/- 5.3% of total urinary conjugates from males and females, respectively). Renal conjugation of p-nitrophenol in vivo was determined using the "Specific Activity Difference Ratio" technique. During infusion of 2 mumol/min/kg of p-nitrophenol, 897.9 +/- 26.0 nmol/min/kg of in vivo formed p-nitrophenylglucuronide was excreted in the urine of female rats whereas 715.6 +/- 65.9 nmol/min/kg was excreted in males.(ABSTRACT TRUNCATED AT 250 WORDS)

Gentamicin and other aminoglycoside antibiotics in high doses may produce proteinuria and other signs of nephrotoxicity. Proteinuria may result from general renal damage or may reflect alterations in specific steps in the renal handling of proteins. To distinguish between these two possibilities, experiments were designed to quantify the effects of nephrotoxic doses of several aminoglycosides on the renal handling of proteins in the isolated perfused rat kidney with the cationic low-molecular-weight protein lysozyme as a representative protein. Each aminoglycoside was administered ip to male Wistar rats (30 mg/kg/day) for 7 days. Lysozyme and 125I-lysozyme were added to the perfusate to achieve a lysozyme perfusate concentration of about 100 mg/liter. Clearances of inulin and lysozyme, release of tyrosine and trichloroacetic acid-soluble radioactive metabolites into the perfusate, and the glomerular sieving coefficient of lysozyme were determined. Scanning and transmission electron microscopy indicated that gentamicin and tobramycin decreased the number and diameter of the endothelial fenestrae of the glomerular capillaries. Concurrently, gentamicin and tobramycin decreased the glomerular sieving coefficient of lysozyme from 0.8 to 0.6 and 0.5, respectively. Netilmicin did not affect the percentage reabsorption of lysozyme whereas gentamicin and tobramycin decreased lysozyme reabsorption from 71.7 to 35.4 and 34.4% of the filtered load, respectively. Lysozyme degradation, estimated by the release of tyrosine into the perfusate during a 150-min perfusion period, was decreased from a control value of 12 mumol/liter to 4.43 and 4.65 mumol/liter in kidneys from rats treated with gentamicin and tobramycin, respectively. This study demonstrates that polycationic aminoglycosides may affect several processes involved in renal handling of lysozyme including glomerular permeability, tubular reabsorption, and intracellular proteolytic degradation.

The aminoglycosides gentamicin, netilmicin and tobramycin were each administered (30 mg/kg/day) to male Wistar rats for 21 days. At 7, 14 and 21 days rats were anesthetized and renal clearances of inulin and egg-white lysozyme were quantified. Plasma concentration of lysozyme varied between 20 and 120 mg/liter in control and aminoglycoside treated rats. Inulin clearance (GFR) averaged 0.96 ml/min/kidney in control rats. Whereas GFR decreased to an average value of 0.47 ml/min/kidney in gentamicin treated rats, GFR did not fall in tobramycin treated rats, averaging 0.97 ml/min/kidney over the entire treatment period. In netilmicin rats GFR declined to 0.53 ml/min/kidney after 7 days of treatment and then increased to 0.78 ml/min/kidney after 14 days and 21 days of treatment. Reabsorption of lysozyme averaged about 94% of the filtered load in control rats. Reabsorption of lysozyme decreased in gentamicin treated rats to about 58% after 7 days and 14 days of treatment and increased to 79% after 21 days of treatment. After tobramycin reabsorption of lysozyme decreased to about 67% after 7 days of treatment and increased to 85% after 14 days and 21 days of treatment. Reabsorption of lysozyme remained unchanged when compared to controls over the entire treatment period in netilmicin treated rats. Thus, gentamicin reduced both GFR and renal reabsorption of lysozyme. Netilmicin reduced GFR somewhat without altering lysozyme reabsorption whereas tobramycin compromised lysozyme reabsorption without altering GFR. These differences might suggest differences in site(s) of action of various aminoglycosides.

Angiontensin-converting enzyme (ACE) catalyzes rapid conversion of angiotensin II (AII). This enzyme has been identified in the vascular endothelium of nearly every tissue. Inasmuch as AII is the biologically active component of the renin-angiotensin system, and since age-related differences exist in the renin-angiotensin system, it was of interest to determine converting enzyme activity during development. ACE activity was quantified by measuring the optical density of hippuric acid liberated from hippuryl-L-histidyl-L-leucine (HHL) following incubation with the 20,000 X g supernatant of tissue homogenates. Pulmonary ACE activity of near-term fetal rats was not different than 1-day-old animals. Therafter, ACE activity increased during the first 6 wk postpartum in a biphasic manner. A similar age-dependent increase in converting enzyme activity was observed in rat kidney, mouse kidney, and mouse lung. Substrate affinity of all enzymes measured was similar, suggesting that the age-related increase in activity was due to increased enzyme content. The low activity of ACE in the newborn might function to limit AII production.

Cephaloridine and gentamicin are selectively accumulated in renal cortex and produce necrosis or proximal tubular cells. However, the mechanisms responsible for renal cortical accumulation of these two antibiotics are quite different; therefore the early pathogenetic processes may not be the same. In the present study, effects of two cephalosporins (cephaloridine and cephalothin) and an aminoglycoside (gentamicin) on rat renal cortical glutathione were determined. Cephaloridine produced a dose-related depletion of renal cortical glutathione one hour following a single administration of the drug. In contrast, cephalothin in equivalent doses did not reduce renal cortical glutathione. Gentamicin had no effect on renal cortical glutathione, even when an acutely lethal dose (1000 mg/kg) was used. Pretreatment of rats with diethyl maleate (0.4 ml/kg) markedly depleted renal cortical glutathione and this pretreatment also potentiated cephaloridine nephrotoxicity. These results suggest that glutathione may play a protective role against cephaloridine but not gentamicin nephrotoxicity.

Carbonic anhydrase is a zinc metalloenzyme whose activity may be affected by zinc deficiency. This investigation was designed to evaluate the effect of zinc deficiency on the response to three diuretic drugs which vary in their capacity to inhibit carbonic anhydrase: acetazolamide, furosemide and hydrochlorothiazide. The response of the zinc-deficient rats was compared to that of pair-fed and ad libitum zinc-supplemented controls. The pattern of electrolyte excretion by zinc-deficient rats in response to the three diuretics was qualitatively similar to that of the pair-fed and zinc-supplemented rats. When corrected for differences in body weight between the three groups, the natriuretic response to the diuretics in zinc-deficient rats was greater than that of either the pair-fed or zinc-supplemented controls. Although administration of the diuretics increased potassium excretion in all groups, the response of the zinc-deficient rats was attenuated. These differences in the response of zinc-deficient rats to diuretics did not appear to be related to the capacity of these drugs to inhibit carbonic anhydrase.

The isolated perfused rat kidney was used to determine whether sex differences in gentamicin nephrotoxicity are related to intrinsic differences in renal response to gentamicin. Acute exposure to gentamicin decreased fractional reabsorption of water and electrolytes without changes in glomerular filtration rate in both sexes. Gentamicin decreased the tubular reabsorption of lysozyme but not glomerular permeability to lysozyme. No sex differences in renal responses were observed following in vitro exposures to gentamicin, suggesting that sex differences in susceptibility to gentamicin in vivo may be attributable to extrarenal factors, such as pharmacokinetics.

Piperonyl butoxide has been shown to reduce accumulation of cephaloridine in rabbit renal cortex; however, the mechanism responsible for this effect remains unclear. Cephaloridine is a zwitterion and its accumulation in renal cortex has been suggested to be regulated by both organic anion and cation transport systems. Thus, it was of interest to determine the effect of piperonyl butoxide on renal transport of p-aminohippurate (PAH, an organic anion) and tetraethylammonium (TEA, an organic cation). Although pretreatment with piperonyl butoxide markedly inhibited renal cortical uptake of cephaloridine, the same treatment had less inhibitory effect on either PAH or TEA uptake. Efflux of PAH from preloaded renal cortical slices was enhanced by pretreatment with piperonyl butoxide; however, TEA efflux was unaffected. Thus, piperonyl butoxide appears to have effects on renal membrane functions which result in differential effects on PAH, TEA, and cephaloridine transport.

This investigation was undertaken to determine the nature of acute alterations in renal function following the production of hypoxemia, hypercarbia, and acidosis in newborn piglets 6-96 hr of age. After completion of the surgical procedure piglets were allowed to recover from the effects of anesthesia. When respiratory dead space was increased arterial oxygen tension decreased whereas arterial carbon dioxide tension and hydrogen ion concentration increased. There was little change in glomerular filtration rate. Total renal blood flow decreased and renal vascular resistance increased significantly (504 +/- 78 mm Hg/liter/mm/m2 to 1422 +/- 504). There was no change in distribution of intrarenal blood flow. Sodium excretion and urinary flow rate demonstrated significant parallel increases following the increase in dead space. Plasma renin concentration increased from 67 to 110 ng/ml.