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Polybrominated biphenyls (PBBs) cause hepatic microsomal enzyme stimulation and histopathological alterations in several organs, including kidney. Concern about effects of PBBs on the health of newborns has increased after the discovery of PBBs in milk of nursing mothers. Therefore, it was of interest to investigate the effects of PBBs on kidney function and the activity of renal microsomal enzymes in adult and immature animals. Seven and eleven day old pups were treated with a single IP injection of either peanut oil or 150 mg/kg PBBs (FireMaster BP-6) in peanut oil. Adult virgin rats were fed diet containing 0 or 100 ppm PBBs for 30 or 90 days. Treatment with PBBs only retarded weight gain after 90 days exposure. Kidney-to-body weight ratio was not altered by PBBs. Arylhydrocarbon hydroxylase activity was increased while epoxide hydratase activity was decreased (adults) or not affected (immature rats) in kidney following treatment with PBBs. Administration of PBBs had no effect on blood urea nitrogen, the clearance of inulin, p-aminohippurate (PAH), or fractional sodium excretion. Similarly, the in vitro accumulation of PAH and N-methylnicotinamide (NMN) by thin renal cortical slices and ammoniagenesis and gluconeogenesis in renal cortical slices were not affected by PBBs. In conclusion, treatment with PBBs resulted in modification of the activity of renal microsomal enzyme activities but had no detectable effect on renal function.

Fast atom bombardment (FAB) is useful for the characterization of all major metabolites of the analgesic acetaminophen (APAP). It is particularly useful for providing mass spectra of the polar glucuronide and sulfate conjugates which eluded identification by field desorption and other more conventional methods of ionization. A protocol is described for the use of FAB in the identification of urinary APAP metabolites isolated by reversed phase high-performance liquid chromatography (HPLC) following therapeutic dosages of the drug. A tentative set of recommendations for the off-line use of HPLC and FAB is directed towards solving problems encountered when using these two analytical techniques in concert. In addition, a method for calculating the signal to background ratio (S/B) for analyte peaks in FAB spectra from selected relative ion intensities is proposed. Examples are presented that show the potential of S/B as an empirical parameter for judging the quality of FAB spectra.

Previous renal clearance studies provided quantitative data concerning renal reabsorption of proteins while the simultaneous processes of renal accumulation and degradation remain, to a great extent, insufficiently investigated. Thus, it was the aim of this study to measure renal reabsorption of egg-white lysozyme at various lysozyme concentrations and to relate the corresponding accumulation and degradation of lysozyme to the lysozyme transport rates in intact rats and isolated perfused rat kidneys. Lysozyme (with 125I-lysozyme in certain experiments), was continuously infused i.v. or added to the perfusate to achieve plasma (or perfusate) concentrations of lysozyme (PLY) of approximately 50, 500 or 1000 mg X 1(-1) for periods of time varying between 3 and 120 or 150 min. Clearances of inulin and lysozyme or the total content of radioactivity and the trichloroacetic acid (TCA)-soluble radioactivity in the kidney tissue were determined at the end of clearance or accumulation periods. Additionally the perfusate concentration of the metabolite tyrosine was measured by high performance liquid chromatography (HPLC). The reabsorption rates of lysozyme (TLY) were concentration-dependent in both intact rats and isolated perfused rat kidney. After 25 min of lysozyme infusion, the lysozyme reabsorption rates amounted to 37, 245 and 331 micrograms X min-1 X g-1 kidney at the above lysozyme concentrations. After the same infusion time, the accumulation rates of lysozyme were 8, 59 and 118 micrograms X min-1 X g-1 kidney. The difference between the transport rate and accumulation rate should represent the renal degradation rate of lysozyme.(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to evaluate the hypothesis that nonesterified fatty acids (NEFA) are endogenous inhibitors of renal organic anion transport and that changes in renal NEFA content could modulate renal organic anion transport capacity. The addition of 1 mM palmitate to a suspension of renal tubules produced a tissue NEFA content of 665 +/- 105 micrograms/g and a 40% decrease in the tissue-to-medium concentration ratio for p-aminohippurate. Penicillin pretreatment enhanced p-aminohippurate tissue-to-medium concentration ratio in a neonatal rabbit proximal tubule suspension but failed to alter renal NEFA content from a control of 46.4 +/- 2.6 micrograms/g. Penicillin treatment did, however, decrease renal triglyceride content and increased serum NEFA from 87.7 +/- 3.4 to 129 +/- 6.8 micrograms/ml. Fasting increased serum triglyceride and increased serum NEFA from 33.9 +/- 3.1 to 370 +/- 200 micrograms/ml. Fasting decreased p-aminohippurate transport capacity 42% from a control tissue-to-medium concentration ratio of 6.78 +/- 1.2 but did not alter renal NEFA from a control value of 65 +/- 15 micrograms/g. The data support the suggestion that penicillin treatment can alter lipid metabolism in vivo but fail to support the suggestion that altered renal organic anion transport is due to altered renal NEFA content and further suggest that NEFA can alter renal organic anion transport only at a supraphysiological concentration.

Male Fischer 344 rats were killed at various times after single or multiple treatments with polybrominated biphenyls (PBB), polychlorinated biphenyls (PCB), sodium phenobarbital (NaPB) or 3-methylcholanthrene (3MC). p-Chloro-N-methyl-aniline N-demethylase (PCNMA) and aryl hydrocarbon hydroxylase (AHH) activities were determined in the 14 000 g supernatant fraction (postmitochondrial supernate, PMS) of renal, testicular and hepatic homogenates. Cytochrome P-450 (p-450) concentrations were determined in the 100 000 g pellet fractions of the same homogenates and the effects of enzyme induction on the sensitivities of AHH in PMS to inhibition by alpha-napthoflavone (ANF) and metyrapone (MET) in vitro were determined. Single treatments with PBB or PCB induced hepatic P-450 only, while multiple treatments with PBB, PCB or 3MC induced both renal and hepatic P-450; NaPB induced only hepatic P-450, while testicular P-450 concentration was unaffected by the inducers. Treatments with PBB, PCB or 3MC shifted the Soret maxima of renal and hepatic dithionite-reduced P-450 difference spectra to shorter wavelengths. Multiple treatments with PBB, PCB or 3MC increased renal and hepatic AHH activities, but NaPB induced hepatic AHH only. Renal AHH activity was increased more rapidly than hepatic AHH after a single treatment with PBB, PCB or 3MC and returned more rapidly to control. The renal AHH induced by PBB and PCB, like that induced by 3MC, was more sensitive to inhibition by ANF in vitro than was renal AHH from naive rats. Hepatic AHH induced by PBB and PCB, unlike that induced by NaPB or 3MC, exhibited no net alterations in sensitivities to the inhibitory effects of ANF or MET. Testicular AHH activity was not induced by PBB, PCB , NaPB or 3MC. Multiple treatments with PBB, PCB or NaPB increased hepatic, but not renal or testicular PCNMA activities. The organ-specificity and time-dependency of the effects of PBB, PCB, NaPB and 3MC on P-450 concentrations and AHH activities suggest that drug metabolism in kidney, testis and liver are regulated by separate control mechanisms. It may be possible to exploit such differences in organ response to enzyme inducers as tools with which to discern the roles of local metabolism in renal and testicular chemical injury.

To investigate the influence of angiotensin II (AII) and renal prostaglandins on neonatal renal hemodynamics and sodium excretion, unanesthetized piglets 1-5, 18-20, and 45-50 days of age were treated with saralasin and indomethacin prior to volume expansion (VE) with isotonic saline. Saralasin did not affect basal renal blood flow (RBF) or the intrarenal distribution of blood flow as calculated as the ratio of outer-to-inner slice counts (O/I) in piglets 1-50 days of age. VE increased fractional sodium excretion equally in all animals. In 1- to 5-day-old piglets, saralasin blunted this natriuresis without affecting renal hemodynamics. Therefore, low neonatal RBF and O/I do not appear to be due to AII. In addition, indomethacin did not change renal hemodynamics in newborn piglets and did not affect the natriuresis after VE in any age group. Indomethacin decreased RBF and increased O/I of conscious 45- to 50-day-old animals. Renal prostaglandins do not appear to be a factor in control of renal hemodynamic in newborn pigs and do not influence the natriuresis in neonates following saline loading.

Synthesis of prostaglandin E2 by renal medulla from SHR and WKY rats was compared during early postnatal development. Although arterial blood pressure was significantly higher in SHR as early as 6 weeks of age, no difference in renal medullary prostaglandin synthesis was observed.

The effect of dietary trans-stilbene oxide (TSO) on hepatic and renal xenobiotic metabolizing-enzyme activities and bromobenzene-induced toxicity was quantified in adult male Sprague-Dawley rats. Rats were fed a regular diet or the same diet supplemented with 2.5 g TSO/kg diet for 10 days. TSO treatment did not alter hepatic or renal arylhydrocarbon hydroxylase activity, but significantly increased glutathione S-transferase and uridine diphosphoglucuronyl transferase activities in both organs. In addition, TSO increased hepatic, but not renal, epoxide hydrolase activity. The same treatment did not produce adverse effects on renal or hepatic functions, but markedly potentiated bromobenzene hepatotoxicity. A single dose of bromobenzene (0.2 ml/kg) caused a slight increase in serum glutamic pyruvic transaminase (SGPT) activity and minor hepatic necrosis in animals fed the control diet; the same dose of bromobenzene markedly increased SGPT activity and produced severe hepatic necrosis in the TSO-fed animals.

The effects of anesthetic agents, nitrous oxide-oxygen, nitrous oxide-oxygen plus ketamine, pentobarbital sodium and halothane, were determined in piglets 6 to 76 hr of age. After observations of cardiovascular and renal function in the unanesthetized state, the drugs were administered and observations were repeated in the anesthetized state. All of the anesthetics caused a decrease in cardiac output and an increase in total peripheral resistance in the newborn piglet. Both nitrous oxide-oxygen plus ketamine and halothane produced a decrease in heart rate while pentobarbital caused an increase and halothane a decrease in systemic blood pressure. Changes in renal function were minimal. Changes in renal blood flow were inconsistent and renal vascular resistance was not modified by any of the drugs. There was little evidence of redistribution of intrarenal blood flow and no significant changes in glomerular filtration rate or sodium excretion. Plasma renin concentration increased after halothane. It was concluded that changes in renal and cardiovascular function due to anesthesia in the newborn were small. Differences between newborn and adult animals may be related to several factors including the state of development of the autonomic nervous system and species differences used in different studies.

In vitro studies with male ICR mouse renal cortical slices have indicated that chloroform (CHCl3) is metabolized by the kidney to a nephrotoxic intermediate, possibly by a cytochrome P-450-dependent mechanism similar to that occurring in the liver. In this investigation, metabolism of 14CHCl3 by microsomes prepared from renal cortex and liver provided definitive evidence for a role of cytochrome P-450 in the renal metabolism and toxicity of CHCl3. 14CHCl3 was metabolized to 14CO2 and covalently bound radioactivity by male renal cortical microsomes; metabolism required oxygen, a NADPH regenerating system, was dependent on incubation time, microsomal protein concentration, and substrate concentration, and was inhibited by carbon monoxide. Consistent with the absence of CHCl3 nephrotoxicity in female mice, little or no metabolism of 14CHCl3 by female renal cortical microsomes was detected. CHCl3 produced a type I binding spectrum with oxidized male renal cortical and hepatic microsomes. Incubation of glutathione with microsomes and 14CHCl3 increased the amount of aqueous soluble metabolites detected with a concomitant decrease of metabolism to 14CO2 and covalently bound radioactivity, suggesting the formation of a phosgene conjugate as has been described for hepatic CHCl3 metabolism. These data support the hypothesis that renal cytochrome P-450 metabolizes CHCl3 to a nephrotoxic intermediate.

Sodium vanadate is a potent inhibitor of Na-K-adenosine triphosphatase. p-Aminohippurate (PAH) and tetraethylammonium accumulation in rat renal cortical slices was inhibited by vanadate in a dose-dependent manner at medium vanadate concentrations from 10(-6) to 10(-3) M. Inhibition was reversible at vanadate concentrations less than 1.5 x 10(-5) M. The slice content of vanadium (7.5-325 micrometer V/g wt. of tissue) was linearly related to medium vanadate concentrations ranging from 10(-5) to 10(-3) M. The ability of slices to generate glucose and ammonia was not impaired by medium vanadate concentrations up to 5 x 10(-4) M, a concentration that maximally inhibited organic ion accumulation. Increasing medium K+ concentrations potentiated vanadate inhibition of PAH accumulation which correlated with inhibition of sodium pump activity, as determined by 42K+ uptake. Intraperitoneal administration of vanadate (1 or 5 mg V/kg) to rats produced a profound diuresis and natriuresis during the 1st hr. Inhibition of PAH accumulation of renal slices from these rats was related to tissue vanadium concentrations. These data suggest that vanadate exerts its action on proximal tubule transport of PAH via inhibition of Na-K-adenosine triphosphatase.

The concentration-dependent abilities of SKF 525-A, metyrapone (MET), piperonyl butoxide (PB), allyl-isopropylacetamide (AIA) and alpha-naphthoflavone (7,8-benzoflavone; ANF) to inhibit the activities of p-chloro-N-methylaniline-N-demethylase (PCNMA) and aryl hydrocarbon hydroxylase (AHH) in vitro were determined in microsomal and postmitochondrial supernatant (PMS) fractions of homogenates prepared from kidneys and livers of rats and mice. Renal microsomal AHH was less sensitive to modulation by SKF 525-A, MET and ANF in vitro than was hepatic microsomal AHH, but renal and hepatic microsomal AHH were equisensitive to inhibition by PB. AIA did not inhibit AHH activities in vitro. Renal AHH and PCNMA activities in PMS fractions were less sensitive to inhibition by SKF 525-A, MET and PB than were hepatic AHH and PCNMA activities. The temporal characteristics of enzyme inhibition in vivo were studied in kidneys and livers removed 1, 2, 4 or 12 h after treatment of the animals with 75 mg kg-1 SKF 525-A or 600 mg kg-1 PB. The degree of inhibition of AHH and PCNMA activities produced by i.p. administration of the inhibitors were greater quantitatively in liver PMS than in kidney PMS, and the degree of inhibition of PCNMA activity in both organs was much less than that of AHH activity. The differences in sensitivity of renal and hepatic AHH and PCNMA activities to the inhibitors may have been due to organ-specific differences in the affinities of the inhibitors for interaction with the active site(s) on cytochrome P-450.

I.p. administration of bromobenzene to male mice at doses ranging from 0 to 9.4 mmol/kg resulted in a dose-dependent increase in blood urea nitrogen (BUN) and serum glutamic-pyruvic transaminase (SGPT) activity and a decrease in renal cortical accumulation of para-aminohippurate (PAH) and tetraethylammonium (TEA). Induction of renal and hepatic mixed-function oxidases by beta-naphthoflavone (BNF) did not result in any alterations in the hepatotoxic or nephrotoxic response to bromobenzene. Renal and hepatic non-protein sulfhydryl (NPSH) concentrations were decreased significantly 1 h after administration of bromobenzene (7.5 mmol/kg) and were maximally depleted in both organs to 18% of control after 7 h. Depletion of renal NPSH by bromobenzene was dose-dependent up to 9.4 mmol/kg. Treatment of mice with diethyl maleate (DEM) (0.6 ml/kg) 60 min prior to bromobenzene administration resulted in greater hepatotoxicity, evidenced by increased SGPT, while renal toxicity was unchanged. These data demonstrate that large doses of bromobenzene produce functional alterations in the kidney.

These experiments were designed to examine the mechanisms involved in the renal excretion of the non-nutritive sweetener, saccharin. Renal transport of saccharin in female rats was quantitatively evaluated using renal cortical slices in vitro and renal clearances in vivo. Renal cortical slices actively accumulated saccharin. Accumulation was oxygen dependent, saturable and reduced in the presence of metabolic inhibitors (2,4-dinitrophenol and sodium azide) and other organic anions 1p-aminohippurate (PAH) and probenecid]. Furthermore, addition of acetate or lactate to the medium stimulated saccharin uptake whereas reducing potassium concentration in the medium significantly decreased saccharin accumulation. Addition of saccharin to medium containing PAH and N-methylnicotinamide produced a dose-related depression of PAH accumulation. Although N-methylnicotinamide accumulation also was reduced, the depression was not dose-related. The saccharin/inulin clearance ratio of 3.76 indicates that saccharin, like PAH, undergoes tubular secretion. These findings suggest that the primary route of renal elimination of saccharin is active tubular secretion. It is also suggested that saccharin and PAH may share a common transport system.

A marked species difference exists in the induction of renal and hepatic mixed function oxidase (MFO) activity between rats and rabbits. However, little is known about MFO induction in these organs from other laboratory animals. Male Golden Syrian hamsters and male Hartley guinea pigs were administered phenobarbital (PB) or beta-napthoflavone (BNF) at 70 and 40 mg/kg, respectively, as daily i.p. injections for 4 days. Polybrominated biphenyl (PBB) (Firemaster BP-6) was given as a single i.p. injection (50 mg/kg). Hamster hepatic microsomal ethoxyresorufin-O-deethylase (EROD) and benzphetamine-N-demethylase (BPND) were selectively induced by BNF and PB, respectively. PBB administration induced both hamster hepatic EROD and BPND. In contrast, hepatic microsomal MFO activity from the guinea pig was inducible by PB, PBB and BNF. Renal microsomal MFO activity in both species was inducible by BNF and PBB as arylhydrocarbon hydroxylase and EROD were induced approximately 10-fold. On the other hand, hamster BPND was induced by PB whereas guinea pig MFO activity was unaffected. Total renal cytochrome P-450 content was not affected by any of these inducers in either species. These data demonstrate selective patterns of induction in both hamster and guinea pig liver and kidney suggesting the involvement of multiple forms of cytochrome P-450.

Marked species and sex differences have been observed in the nephrotoxicity to the cephalosporin antibiotic cephaloridine (CPH). Preliminary studies have also indicated significant strain differences in mice to CPH nephrotoxicity. To investigate these findings further, male and female C57BL, BALB/c, CD-1, CFW, CBA/J, and DBA/2 mice were given either 4000 or 6000 mg/kg of CPH, sc. Renal function was assessed 48 hr later by the ability of renal cortical slices to accumulate the organic ions p-aminohippurate (PAH) and tetraethylammonium (TEA), changes in blood urea nitrogen (BUN) and kidney-to-body wt ratios. CPH produced dose-dependent nephrotoxicity in C57BL female mice. After 6000 mg/kg, PAH and TEA slice-to-medium (S/M) ratios were reduced by 70 and 49%, respectively; BUN was elevated 10-fold. The same dose given to CFW females had no effect. BALB/c, CD-1, CBA/J, and DBA/2 females showed intermediate signs of toxicity. Male mice of all strains tested exhibited no nephrotoxicity. CPH nephrotoxicity has been correlated with the concentration of CPH within the tubular cell; and C57BL female mice had relatively greater intracellular accumulation of CPH than C57BL male mice and CFW female mice in vitro and in vivo. Thus, differences in net renal cortical accumulation of CPH suggest possible differences in transport, binding, and/or metabolism of CPH may exist among strains and between sexes of mice.

In 5-, 15-, 30-, and 60-day-old rats there was a distinct decrease of body weight 24 hours after a single i.p. injection of cis-dichlorodiammineplatinum (CDDP) over a dose range from 0.25 to 2.0 mg/100 g b.w.t. Compared with a control group the kidney weights appeared nearly unchanged. The increase of blood urea nitrogen (BUN) concentrations following CDDP treatment was dose dependent and more profound in 5- and 15-day-old rats than in older animals. In higher doses, CDDP impaired the renal concentrating ability in rats of all age groups as reflected in a significant increase in urine volume with only a slightly increased renal sodium excretion. Following CDDP treatment there was a moderate proteinuria. In 30- and 60-day-old rats the renal excretion of p-aminohippurate (PAH) was more reduced by CDDP compared to younger rats.

The effects of indomethacin on furosemide induced changes in renal blood flow were determined in dogs. Furosemide alone caused an increase in total renal blood flow while indomethacin alone decreased renal blood flow. When furosemide was administered to animals pretreated with indomethacin the increase in renal blood flow was blocked. Changes in intrarenal blood flow distribution were also measured using radioactive microspheres. The pattern of blood flow distribution after furosemide was modified in some of the animals pretreated with indomethacin. Stimulation of renin secretion occurred after furosemide in indomethacin-treated animals. The data suggest that the changes in renal blood flow produced by furosemide may be modulated by the prostaglandin system.

Experiments were undertaken to investigate further the effect of furosemide on renin secretion in the anesthetized dog. To separate the effects of the macula densa and the baroreceptor mechanisms, experiments were conducted in kidneys made nonfiltering by combining 2.5 hours of renal ischemia with ureteral ligation. Furosemide, in a dose of 5 mg/kg, increased renin secretion and decreased renal resistance in dogs with a nonfiltering kidney. Prior dilation of the nonfiltering kidney with either acetylcholine or papaverine prevented changes in both resistance and renin secretion. However, following dilation of the intact filtering kidney with acetylcholine, furosemide caused an increase in renin secretion. Infusion of d,l-propranolol decreased renin secretion in both the filtering and the nonfiltering kidneys. Following propranolol treatment, furosemide increased renin secretion in the filtering kidney but had no effect on renal resistance. These experiments indicate that furosemide stimulates renin secretion by both the macula densa and the baroreceptor mechanisms. The data suggest that stimulation of the sympathetic nervous system may alter renin secretion by modulating the renal baroreceptor, but sympathetic innervation does not appear to be involved in the macula densa mechanism.

Administration of chloroform (CHCl3) to male C57/6J (C57) and DBA/2J (DBA) mice produced dose-dependent hepatic and renal damage. Hepatic arylhydrocarbon hydroxylase (AHH) activity was higher in C57 than DBA mice; in kidney, AHH activity was higher in DBA than in C57 mice. CHCl3 caused the same degree of liver damage in both strains of mice; however, nephrotoxicity of CHCl3 was greater in DBA than in C57 mice. Pretreatment of C57 and DBA mice with phenobarbital (PB) markedly increased hepatic AHH activity and hepatotoxicity of CHCl3 in both strains but did not affect renal AHH or nephrotoxicity of CHCl3. Similarly, beta-naphthoflavone (BNF) enhanced AHH activity and CHCl3 hepatotoxicity in C57 mice, but had little effect on nephrotoxicity. BNF did not affect hepatic AHH nor CHCl3-induced hepatic injury in male DBA mice. Pretreatment with polybrominated biphenyl (PBB) enhanced AHH activity in liver and CHCl3 hepatotoxicity in both strains. After PBB, nephrotoxicity of CHCl3 and renal AHH activity were increased in C57 mice whereas PBB did not alter nephrotoxicity or renal AHH in DBA mice. These results suggest that CHCl3-nephrotoxicity is independent of hepatotoxicity.

The effects of development of renal function on the response of newborns to furosemide was evaluated in an animal model, the newborn piglet. Three ages of piglets were used: 5-day-old, 20-day-old, and 50-day-old. Intravenous administration of furosemide (2 mg/kg) produced a prompt natriuresis in all animals. The natriuresis after furosemide was greatest in the older piglets (110 microEq/min for 50-day-old piglets were 210 microEq/min for 5-day-old piglets). However, the fractional sodium excretion at the peak of the response was near 20% in animals in each age group. Neither the time of peak response nor duration of natriuresis was affected by age. Potassium excretion increased after furosemide and remained elevated after both urine flow and sodium excretion had returned to control. The pattern of potassium excretion was identical for each of the three age groups. Thus, while renal maturation does not markedly affect the response to furosemide, both newborns and older piglets continue to excrete relatively large amounts of potassium after sodium excretion returns to control.

Since neuronal lesions produced by aluminum (Al) are morphologically similar to lesions produced by microtubule inhibitors, the effect of aluminum on microtubule integrity was investigated. Aluminum inhibited microtubule formation at concentrations as low as 0.1 mM. This approaches the aluminum concentrations found in brains of patients with several disorders which result in progressive dementia.

Renal cortical necrosis induced by acetaminophen (APAP) may be related to generation of reactive intermediates by two mechanisms of metabolic activation, direct P-450 dependent metabolic activation (P-450) or metabolic activation subsequent to deacetylation of APAP to p-aminophenol (PAP). Generation of arylating intermediates by both pathways of metabolic activation was quantified in cyclohexamide (HEX)-pretreated or naive rats in vivo with specifically labeled [14C]APAP. The association of each type of metabolic activation with APAP-induced nephrotoxicity was determined in Fischer 344 (F344) and Sprague-Dawley (SD) rats, strains that are susceptible and resistant to APAP-induced nephrotoxicity, respectively. Covalent binding of [ring-14C]APAP to renal cortex was approximately four times greater than [acetyl-14C]APAP in HEX-pretreated F344 rats. In contrast, in SD rats pretreated with HEX covalent binding of [ring-14C]APAP and [acetyl-14C]APAP in the renal cortex was not different. Furthermore, covalent binding of [ring-14C]APAP to renal cortical protein was approximately four times greater in F344 rats than in SD rats. Arylation of hepatic protein by either [ring-14C]APAP or [acetyl-14C]APAP was similar regardless of strain or pretreatment regimen. These studies demonstrated arylation of renal macromolecules in vivo by reactive intermediates resulting from PAP in F344 but not SD rats. Since F344, but not SD, rats are susceptible to APAP-induced nephrotoxicity, it appears the formation of arylating intermediates by PAP is a requisite step in APAP-induced nephrotoxicity.

Large doses of the cephalosporin antibiotic, cephaloridine, produce acute proximal tubular necrosis in humans and in laboratory animals. Cephaloridine is actively transported into the proximal tubular cell by an organic anion transport system while transport across the lumenal membrane into tubular fluid appears restricted. High intracellular concentrations of cephaloridine are attained in the proximal tubular cell which are critical to the development of nephrotoxicity. There is substantial evidence indicating that oxidative stress plays a major role in cephaloridine nephrotoxicity. Cephaloridine depletes reduced glutathione, increases oxidized glutathione and induces lipid peroxidation in renal cortical tissue. The molecular mechanisms mediating cephaloridine-induced oxidative stress are not well understood. Inhibition in gluconeogenesis is a relatively early biochemical effect of cephaloridine and is independent of lipid peroxidation. Furthermore, cephaloridine inhibits gluconeogenesis in both target (kidney) and non-target (liver) organs of cephaloridine toxicity. Since glucose is not a major fuel of proximal tubular cells, it is unlikely that cephaloridine-induced tubular necrosis is mediated by the effects of this drug on glucose synthesis.

Rat renal microsomes catalyzed the glucuronidation of l-naphthol, 4-methylumbelliferone and p-nitrophenol, whereas morphine and testosterone conjugation were not detected. In contrast, all five substrates were conjugated by hepatic microsomes; the activity was typically 5-10 times greater than with renal microsomes. Renal microsomal UDP-glucuronyltransferase toward l-naphthol was fully activated (six-fold) by 0.03% deoxycholate while the hepatic enzyme was fully activated (eight-fold) by 0.05% deoxycholate. Full activation of hepatic UDP-glucuronyltransferase occurred when microsomes had been preincubated at 0 C with deoxycholate for 20 min. This effect of preincubation was not observed with renal microsomes. The presence of 0.25M sucrose in the buffers during renal microsomal preparation resulted in a two-fold greater rate of l-naphthol conjugation in both unactivated and activated microsomes than renal microsomes prepared in phosphate buffers alone. Preparation of hepatic microsomes with or without 0.25M sucrose had no effect on UDP-glucuronyltransferase activity. Unactivated (-deoxycholate) renal enzyme was activated when incubations were done at a low pH (5.7), whereas fully activated (0.03% deoxycholate) renal microsomal UDP-glucuronyltransferase displayed a pH optimum at 6.5. Renal microsomal UDP-glucuronyltransferase activity toward l-naphthol, p-nitrophenol and 4-methylumbelliferone was induced by pretreatment of rats with beta-naphthoflavone and trans-stilbene oxide but not by phenobarbital or 3-methylcholanthrene. These data demonstrate that renal UDP-glucuronyltransferases are different from the hepatic enzymes with regard to biochemical properties, substrate specificity and in response to chemical inducers of xenobiotic metabolism.

Body weight gain and hepatic concentrations of vitamin A were reduced in Sprague-Dawley rats by pre- and postnatal exposure to 100 ppm polybrominated biphenyls (PBBs). The ratio of liver weight to body weight, activity of hepatic delta-aminolevulinic acid (ALA) synthetase, and urinary excretion of uro- and coproporphyrins were increased by PBBs. Treatment with PBBs also increased the left atrial inotropic response to calcium. However, PBBs had no effect on development of the adrenergic neuronal transport system in heart, left atrial baselike peak tension, or inotropic response to ouabain. Thus PBBs retarded body weight gain and produced a variety of alterations in liver, but had little effect on cardiac contractile function.

Dinoseb has produced alterations that are suggestive of renal damage in mice and rats. Therefore it was of interest to determine the postnatal morphology and functional capacity of the kidney following prenatal treatment with dinoseb in rats. Fetal and neonatal rats treated with dinoseb on gestational d 10-12 had dilated renal pelves and ureters. Kidneys had dilated tubules and excessive mesenchymal tissue when examined perinatally. These pathological changes were reduced in incidence (kidney) or not detected (ureter) at 42 d postpartum and were not correlated with alterations in postnatal renal function. Livers from rats treated prenatally with dinoseb were vacuolated and necrotic even at 42 d postpartum. Rats treated prenatally with dinoseb had reduced body weights at 1 and 7 d postpartum. However, body weights of control and dinoseb-treated rats were not significantly different at 42 d of age. These results emphasize the need to determine the pesistence and functional consequences of anomalies detected in near-term fetuses for safety assessment of a chemical.

Plasma renin activity (PRA) was determined in conscious piglets between 1 and 50 days of age before and after treatment with saralasin and indomethacin. Following drug treatment, animals were volume expanded with isotonic saline. Saralasin increased PRA in piglets 1-5 and 18-22 days of age but not 45-50 days. Neither indomethacin nor VE changed PRA at any age. Volume expansion of saralasin- and indomethacin-treated pigs decreased PRA. Neonatal hyperreninemia does not appear to result from renin release stimulated by prostaglandins or by the absence of angiotensin II negative feedback. In addition, the plasma half-life of renin was not different between young and more mature animals suggesting that immature hapatic metabolism of renin cannot be entirely responsible for the high PRA in newborns.

Acetaminophen (APAP) produces proximal tubular necrosis in Fischer 344 (F344) rats. Recently, p-aminophenol (PAP), a known potent nephrotoxicant, was identified as a metabolite of APAP in F344 rats. The purpose of this study was to determine if PAP formation is a requisite step in APAP-induced nephrotoxicity. Therefore, the effect of bis(p-nitrophenyl) phosphate (BNPP), an acylamidase inhibitor, on APAP and PAP nephrotoxicity and metabolism was determined. BNPP (1 to 8 mM) reduced APAP deacetylation and covalent binding in F344 renal cortical homogenates in a concentration-dependent manner. Pretreatment of animals with BNPP prior to APAP or PAP administration resulted in marked reduction of APAP (900 mg/kg) nephrotoxicity but not PAP nephrotoxicity. This result was not due to altered disposition of either APAP or acetylated metabolites in plasma or renal cortical and hepatic tissue. Rather, BNPP pretreatment reduced the fraction of APAP excreted as PAP by 64 and 75% after APAP doses of 750 and 900 mg/kg. BNPP did not alter the excretion of APAP or any of its non-deacetylated metabolites nor did BNPP alter excretion of PAP or its metabolites after PAP doses of 150 and 300 mg/kg. Therefore, the BNPP-induced reduction in APAP-induced nephrotoxicity appears to be due to inhibition of APAP deacetylation. It is concluded that PAP formation, in vivo, accounts, at least in part, for APAP-induced renal tubular necrosis.

Incubation of renal cortical slices with cephaloridine (CPH) markedly inhibits pyruvate-supported gluconeogenesis, an effect which is independent of CPH-induced lipid peroxidation. CPH was found to inhibit pyruvate-supported gluconeogenesis in a time-and concentration-dependent manner. Pyruvate-supported gluconeogenesis was inhibited as early as 10 min following incubation of renal cortical slices with 5 mM CPH. Similarly, endogenous gluconeogenesis was impaired following CPH treatment. CPH depressed the renal cortical slice content of ATP by 50%, but only following 90 and 120 min of drug exposure, suggesting that mitochondrial dysfunction does not mediate the inhibition of gluconeogenesis by CPH. To identify the intracellular site(s) of CPH inhibition of gluconeogenesis, the effects of CPH on glucose production were evaluated using substrates catalyzed by rate-limiting reactions. CPH inhibited renal cortical slice gluconeogenesis when the following substrates were used: pyruvate (mitochondrial), oxaloacetate and fructose-1,6-diphosphate (FDP) (postmitochondrial), and glucose-6-phosphate (G6P, endoplasmic reticulum). Inhibition of G6P-supported gluconeogenesis occurred within 5 min of incubation with 5 mM CPH. Direct addition of CPH to microsomal suspensions inhibited G6Pase activity in a concentration-dependent fashion. By contrast, addition of CPH to cytosolic fractions did not affect FDPase activity. CPH increased the Km and decreased the Vmax of G6Pase, indicating mixed competitive and noncompetitive inhibition. These data indicate that the profound inhibition of renal cortical slice gluconeogenesis by CPH is mediated by inhibition of microsomal G6Pase activity.