Toxicological studies on 2,4,6-tribromoanisole.

TBA, or 2,4,6-tribromoanisole, is a musty-smelling metabolite of 2,4,6-tribromophenol that is used as a flame retardant and an antifungal agent for wooden pallets and packaging materials. The compound can impart its peculiar, often offensive, odor on product packaging to the concern of consumers for the safety of the package contents. These studies were conducted to evaluate the safety of TBA to humans ingesting products tainted with TBA. In addition to the 28-day oral study, a bacterial reverse mutation study was conducted, and confirmed that TBA was not mutagenic. To evaluate oral safety, TBA was evaluated in single dose and 5-day and 4-week repeated dose oral toxicity studies in rats. The test article, administered in single gavage doses of 2000, 5000 and 7500 mg/kg body weight (bw), in 5 daily repeated doses of 1000, 2000 or 3000 mg/kg bw/day or in 28 daily oral gavage doses of 0 001, 0.01, 100, and 1000 mg/kg bw/day did not result in any deaths. Also, the single and repeat dose studies resulted in no significant differences between control and treated groups on body weight gain, food consumption, clinical observations, blood biochemical values, and hematology findings. Treatment-related adverse findings were only detected in male rats during repeated dose studies and were associated with high plasma concentrations of TBA. The test article-related finding of hyaline droplets in the cortical tubular epithelium of kidneys was associated with increases in α(2 µ)-globulin content in the kidneys as indicated by the intensity of immunohistochemical staining. These findings were correlated with an increased weight of kidneys in males administered 1000mg/kgbw/day for 28days. Chemical induction of hyaline droplets containing α(2µ)-globulin in the renal proximal tubule is a process unique to the male rat and is not relevant for human risk assessment. Findings of increased liver weight with minimal centrilobular to diffuse hepatocellular hypertrophy in males treated with TBA at 1000mg/kg bw/day for 28days were considered to be an adaptive metabolic response to xenobiotic administration. The increased volume of urine, noted in both males and females treated with 1000mg/kg bw/day was considered adaptive and necessary to excrete the high xenobiotic burden resulting from TBA administration. TBA appeared to be highly bioavailable since high concentrations of TBA were detected in plasma, at 1, 4 and 8h after administration of TBA at 100 and 1000mg/kg bw for 1 and 28days. Levels were dose-related but did not clarify the course of TBA elimination with time after administration. These studies indicate that TBA, administered orally to rats, produced male rat-specific, treatment-related toxicity at the highest orally administered dose in repeated dose (5-day at 3000mg/kg bw and 28-day at 1000mg/kg bw) studies. Therefore, the NOAEL for the 28-day oral study was determined to be 1000mg/kg bw/day for the rat.

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic cracked naphtha distillate in rats.

A 15-week, whole-body inhalation study of the vapors of a distillate (LCCN-D) of light catalytic cracked naphtha (CAS no. 64741-55-5, LCCN) was conducted with Sprague-Dawley rats. Target exposure concentrations were 0, 750, 2500, and 7500 ppm for 6 hours/day, 5 days/week. Over the course of the study, animals received at least 65 exposures. For a portion of the control and 7500-ppm groups, a 4-week postexposure period was included in the study. Subchronic toxicity was evaluated using standard parameters. During life, neurotoxicity was evaluated by motor activity assessment and a functional observational battery. Selected tissues from animals in all exposure groups were examined microscopically. Neuropathologic examination of selected neuronal tissues from animals in the control and high-exposure groups was also conducted. No compound-related effects were seen on survival, clinical chemistry, food consumption, or physical signs. No evidence of neurotoxicity was seen at any exposure level. Slight decreases in hematocrit and hemoglobin concentrations were seen in male rats at the end of exposure to 7500 ppm LCCN-D. However, values were within normal physiological ranges and recovery occurred. Slight decreases in mean body weights and body weight gain were observed in high-exposure females during the first 7 weeks of exposure, but this decrease was not seen during the second half of the study. Male rat nephropathy involving hyaline droplet formation and alpha-2micro-globulin accumulation was seen in mid- and high-exposure males, an effect not relevant to humans. The incidence and severity of goblet cell hypertrophy/hyperplasia and respiratory epithelium hyperplasia in nasoturbinal tissues were greater in high-exposure animals, but recovery occurred. None of the effects observed were considered toxicologically significant. The no-observable-adverse-effect level (NOAEL) for subchronic and neurotoxicity of LCCN-D was > or = 7500 ppm.

Developmental toxicity evaluation of unleaded gasoline vapor in the rat.

To evaluate the potential of unleaded gasoline vapor for developmental toxicity, a sample was prepared by slowly heating API 94-02 (1990 industry average gasoline) and condensing the vapor. The composition of this vapor condensate, which comprises 10.4% by volume of the starting gasoline, is representative of real-world exposure to gasoline vapor encountered at service stations and other occupational settings and consists primarily of volatile short chain (C4-C6) aliphatic hydrocarbons (i.e. paraffins) with small amounts of cycloparaffins and aromatic hydrocarbons. A preliminary study in rats and mice resulted in no developmental toxicity in either species. However, a slight reduction in maternal body weight gain in rats led to the selection of rats for this guideline study. Groups of pregnant rats (n = 24/group) were exposed to unleaded gasoline vapor at concentrations of 0, 1000, 3000, or 9000 (75% lower explosive limit) ppm equivalent to 0, 2653, 7960, or 23,900 mg/m3, for 6 h/day on gestation days 6-19. All rats were sacrificed on gestation day 20. No maternal toxicity was observed. Developmentally, there were no differences between treated and control groups in malformations, total variations, resorptions, fetal body weight, or viability. The maternal and developmental NOAEL is 9000 ppm. Under conditions of this study, unleaded gasoline vapors did not produce evidence of developmental toxicity.

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic reformed naphtha distillate in rats.

A distillate of light catalytic reformed naphtha (CAS number 64741-63-5, LCRN-D) administered by inhalation was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening protocol. LCRN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 6 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for approximately 7 consecutive weeks. Dams and litters were sacrificed on postnatal d 4 and males were sacrificed within the week after the last litter was necropsied. Parental systemic effects observed at the 7500 ppm exposure level included slightly lower body weights for males throughout the study. Increased kidney to body weight and increased liver to body weight ratio in male rats exposed to 7500 ppm LCRN-D may be related to slightly lower final mean body weights. Body and organ weight data for female rats in all exposure groups were comparable to controls. No test-material-related microscopic changes were observed in the reproductive organs or nasal turbinate tissue of either sex. Reproductive performance was unaffected by exposure to LCRN-D. The mating and fertility indices were 100% in all groups. There were no significant exposure-related differences in implantation sites or live pups per litter, and no gross abnormalities were observed in pups from treated dams. Pups born from LCRN-D-exposed dams showed comparable body weights and weight gain to control pups. The viability index on postpartum d 4 was > or =97%. Under conditions of this study, the no-observed-adverse-effect level (NOAEL) for exposure to light catalytic reformed naphtha distillate for parental effects was 2500 ppm and the NOAEL for reproductive and developmental toxicity was 7500 ppm.

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic reformed naphtha distillate in rats.

A 13-wk whole-body inhalation study was conducted with Sprague-Dawley CD rats (16/sex/group) exposed to a light catalytic reformed naphtha distillate (LCRN-D, CAS number 64741-63-5) at target concentrations of 0, 750, 2500, and 7500 ppm for 6 h/d, 5 d/wk. Sixteen rats per sex in the control and high-dose groups were maintained after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, throughout exposure and after the recovery period. Neuropathology was evaluated at termination. No test-related mortality or effects on physical signs, body weight, food consumption, or clinical chemistry were observed. In males exposed to 7500-ppm LCRN-D, a statistically significant decrease in white blood cell counts and lymphocyte counts was observed at the termination of exposure that was not present in animals after the 4-wk recovery period. However, mean corpuscular volume was slightly decreased in high-dose males after the recovery period. Statistically significant increases in kidney weights relative to body weights in 7500-ppm male rats correlated with microscopically observed hyaline droplet formation and renal tubule dilation, indicative of light hydrocarbon nephropathy, a condition in male rats that is not toxicologically significant for humans. Statistically significant decrease in absolute and relative spleen weights in 7500-ppm male rats correlated with decreases in hematologic parameters but had no microscopic correlate and was not observed in animals after 4 wk of recovery. This mild, reversible effect in white blood cell populations may relate to the presence of aromatics in the distillate. The only effect of LCRN-D on neurobehavioral parameters was significantly higher motor activity counts among high-dose (7500 ppm) males after the 4-wk recovery period, suggesting a possible delayed effect of LCRN-D. However, there was no evidence of hyperactivity or abnormal behavior from the functional observational battery evaluations, and there were no microscopic changes in neural tissue to support this observation. The no-observed-adverse-effects level (NOAEL) for LCRN-D was 2500 ppm for both subchronic toxicity and neurotoxicity. The no-observed-effects level (NOEL) was 750 ppm.

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic cracked naphtha distillate in rats.

A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in high-dose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. IncreaSed kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related microscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was > or =90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was > or =97%; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.

Toxicity of middle distillates from dermal exposure.

This report focuses on recent studies that investigated the effects of kerosine dermal exposure on neurotoxicity and reproductive/developmental toxicity. Background toxicity information will also be reviewed for kerosine range mid distillates. The kerosine range mid distillates have a carbon range of C9-C16 and have a boiling range of 302-554 degrees F (150-290 degrees C). This category includes kerosine, aviation fuels (e.g., Jet A, JP-5 and JP-8), no. 1 fuel oil and diesel fuel oil. In general, the kerosine range mid distillates demonstrate relatively low acute toxicity by any route of exposure. High inhalation exposures can induce central nervous system depression characterized by ataxia, hypoactivity and prostration. Kerosines are known to cause skin irritation and inflammation under conditions of acute and repeated exposure in animals and humans, but are only slightly irritating to the eye and are not skin sensitizers. In addition, the absorption of kerosine range mid distillates through the skin has been demonstrated to be fairly rapid, but limited to approximately 10-15% of the applied dose after 24 hours. The kerosine range mid distillates are generally inactive in genetic toxicity tests although positive studies have been reported. Positive results, while at times equivocal, have been reported for straight run kerosine and jet fuel A in the mouse lymphoma assay with metabolic activation, and hydrodesulfurized kerosine (mouse) and jet fuel A (rat) in the bone marrow cytogenetic assay. Effects on the nervous and reproductive systems have been reported in humans and experimental animals under conditions where inhalation and dermal exposure to specific kerosine type fuels are sometimes difficult to separate. Recent laboratory studies have addressed this point and examined the effects of dermal exposure. In these studies, rats were exposed to hydrodesulfurized kerosine by skin application to determine the potential of dermal contact to cause reproductive/developmental toxicity (OECD Guideline 421) or neurotoxicity (TSCA Guidelines on subchronic inhalation and neurotoxicity studies). These studies demonstrated that the highest dose level of kerosine does not induce reproductive/developmental or neurotoxicity effects by skin exposure in rodent studies. The dermal NOEL for HDS kerosine in rats was > or = 494 mg/kg for both neurotoxicity, and reproductive/developmental toxicity.

Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light alkylate naphtha distillate in rats.

A 13-wk inhalation study was conducted with Sprague-Dawley CD rats (12/sex/group) were exposed by inhalation for 13 weeks to a light alkylate naphtha distillate (LAND-2, C4-C10; average molecular weight 89.2) at actual average concentrations of 0 (room air), 668, 2220, or 6646 ppm, 6 h/d, 5 d/wk; 12 additional rats/sex in the control and high dose groups were held after final exposure for a 4-wk recovery period. The highest exposure concentration was 75% of the lower explosive limit. Standard parameters of subchronic toxicity were measured throughout the study; at necropsy, organs were weighed and tissues processed for microscopic evaluation. Neurotoxicity evaluations consisted of motor activity (MA) and a functional operational battery (FOB) measured pretest, during 5, 9, and 14 wk of the study, and after the 4-wk recovery period. Whole-body perfusion and microscopic examination of selected organs and nervous tissue from the control and high dose rats were conducted at the end of exposure. No test-related mortality or effects on physical signs, body weight, or food consumption were observed. Statistically significant increases in absolute and relative kidney weights in high-exposure males correlated with microscopically observed hyaline droplet formation and renal nephropathy, effects in male rats that are not toxicologically significant for humans. Increased liver weights in both sexes at the highest dose had no microscopic correlate and appeared reversible after the 4-wk recovery period. Exposure to LAND-2 at any dose did not produce neurotoxicity measured by MA, FOB, or neuropathology. The no-observed-effects level (NOEL) for LAND-2 was 2220 ppm for subchronic toxicity and > or =26646 ppm for neurotoxicity.

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of a distillate from light alkylate naphtha.

A distillate of light alkylate naphtha (CAS number 64741-66-8; LAN distillate) was administered via inhalation, 6 h/d, 7 d/wk to 4 groups of Sprague-Dawley rats (10/sex/dose) at target concentrations of 0 (filtered air control), 5, 12.5, or 25 g/m3 with the highest dose exceeding 60% of the lower explosive limit of LAND. Exposure began 2 wk prior to mating and continued throughout gestation until postnatal d 4 for females or for 8 consecutive weeks for males. No apparent clinical signs indicative of systemic toxicity were observed in the F0 and F1 animals of either sex. Inhalation exposure to LAND up to and including the 25 g/m3 dose level had no effect on parental food consumption, body weights, absolute and relative organ weights, and reproductive indices. All groups had comparable delivery data and a fertility index > or 80%. Pups in all groups showed comparable birth weights, weight gain, a viability index (postnatal d 4) for all groups of > or = 97%, and no histopathological changes. In the dams, there were no significant differences in the mean numbers of corpora lutea, implantation sites, and resorptions recorded at necropsy. In the males, the only remarkable findings at necropsy were a small right epididymis and testis seen in one mid-dose male and an abscess on the right epididymis of a high-dose male. In both cases, the dams that had been bred to these males produced normal litters. There were no test material-related microscopic changes observed in the testes and epididymis of the F0 male rats or ovaries of the F0 female rats exposed to LAND. Under the conditions of this experiment, the no-observed-adverse-effect level (NOAEL) for LAND via inhalation in rats is established at greater than 24.7 g/m3 (analytical concentration).

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of hydrodesulfurized kerosine.

Hydrodesulfurized kerosine (HDS kerosine), applied dermally, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, using a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening Protocol. A preliminary acute dermal irritancy test demonstrated that dilution of HDS kerosine in either a light (100 Saybolt universal seconds, SUS) or moderate viscosity (340 SUS) USP mineral oil reduced irritation of the neat material comparably. Similar dermal absorption was observed in vitro for neat HDS kerosine or diluted in either of the mineral oils. HDS kerosine diluted to 494 (60%), 330 (40%), or 165 (20%) mg/kg/day in Squibb mineral oil (340 SUS) was applied daily at 1 ml/kg to the shaved backs of rats for 7 wk (premating, mating to d 19 of gestation) to females and 8 wk to males. Dams and litters were sacrificed on postpartum d 4 and males were sacrificed within the following week. HDS kerosine produced slight to moderate skin irritation at the highest dose in both sexes but no apparent maternal, reproductive, or developmental toxicity. No clinical signs of toxicity and no effects on body weight, food consumption, or absolute organ weights were observed. Relative kidney weights were heavier in male rats at the high dose. Skin changes were observed microscopically in male rats in all groups and in females at the high dose. No microscopic changes were observed in reproductive organs of parental animals. There were no differences in mean number of corpora lutea, implantation sites, and live pups per litter, and no gross anomalies were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was > or = 93%. In conclusion, the no observable adverse effect level (NOAEL) for HDS kerosine for reproductive and developmental toxicity in rats is 494 mg/kg/d.

Developmental toxicity study of clarified slurry oil (CSO) in the rat.

Pregnant CD rats were exposed dermally to 0.05, 1, 10, 50, and 250 mg/kg/day of Clarified Slurry Oil (CSO) on Days 0-19 of gestation to determine its potential developmental toxicity. Untreated and vehicle controls were included in the study. Day 20 of gestation Caesarean-derived fetuses were examined for gross, external, and visceral or skeletal alterations. Dosages of 1 mg/kg/day and higher significantly decreased maternal body weight, body weight gain, feed consumption, gravid uterine weight, and live litter size and significantly increased resorption rate. These dosages also significantly reduced fetal weights and retarded development of the brain, kidney, thoracic and caudal vertebrae, metacarpals, and hindpaw phalanges in dosage groups with live fetuses (high dosage group dams resorbed all conceptuses). The 50- and 250-mg/kg/day dosage group dams had only placentas and/or dark red viscous fluid in the uterus or vagina and significant body weight loss (associated with resorption). The highest dosage also caused emaciation, slight dehydration, and swollen dark anogenital areas. These results indicate that CSO produces adverse developmental effects at maternally toxic dosages. The maternal and developmental NOAELs (no observed adverse effect levels) were 0.05 mg/kg/day. In a second study, groups of 10 mated female rats were exposed to "pulse" exposures and dosages of 1, 50, or 250 mg/kg/day of CSO applied dermally for 2- or 3-day intervals that spanned the gestation period. All dosages reduced maternal feed consumption and body weight gain during the treatment period. Dosages of 50 and 250 mg/kg/day also produced early resorptions when administered on Days 6 through 8 and 9 through 11 of gestation. However, no increase in fetal alterations occurred, indicating that the effects on embryo-fetal development were due to early death and not to the death of malformed conceptuses.

Effect of dietary administration of the rubber curative trithiocyanuric acid to the rat.

Trithiocyanuric acid (TCY) is a rubber curative of low oral and dermal toxicity and with a low potential for eye and skin irritation. This study determined the effects of TCY on Sprague-Dawley rats at levels of 0.0, 625, 2500 and 5000 ppm in the diet for 2-30 days. While there were some effects on body-weight gain and survival at the higher levels of intake, the main effects concerned unusual lesions of the pinna and the distal portions of the tail. Purplish discolorations of the ear margin and tip of the tail were noted in some animals on the 2500- and 5000-ppm diets. The tail lesion was evident microscopically at day 16 only in the 5000-ppm group and consisted of congestion of the vasculature in the subepidermal connective tissue with focal necrosis of the distal tail segment. By day 16 the ear lesion was also microscopically identifiable only in the group on the 5000-ppm diet. It was found in 33% of these animals at day 8 and in 67% at day 16 and consisted of a localized cellulitis characterized by moderate infiltrates of polymorphonuclear leucocytes in the epidermal and subepidermal tissues. The lesions caused by high levels of TCY were apparently site-specific, since histopathological examination of selected internal organs did not detect any lesions. The no-effect levels determined were 2500 ppm for microscopic lesions during an 8-16-day treatment period and 625 ppm for gross pathological lesions in a 30-day feeding study.

Subchronic feeding study in beagle dogs of N-methylpyrrolidone.

The potential toxicity of N-methylpyrrolidone was evaluated following dietary administration for 13 weeks to male and female beagle dogs at dosage levels of 25, 79 and 250 mg per kg body weight per day. Body weight gain and food consumption, hematological and clinical chemical data, and ophthalmic, gross and histopathological examinations were used to study possible toxicological or pathological effects. No statistically significant treatment-related effects that were judged to be biologically meaningful were seen in any parameters of either male or female animals exposed to N-methylpyrrolidone at any dose level. However, a dose-dependent decrease in body weight and increase in platelet count that correlated with increased megakaryocytes was observed. Serum cholesterol in males decreased with increasing doses.

Concentration-dependent elicitation of dermal sensitization in guinea pigs treated with 2,4-toluene diisocyanate.

2,4-Toluene diisocyanate (TDI) can cause pulmonary sensitization and allergic skin reactions. Since many commercial materials contain TDI, the present study was designed to determine the concentration-dependent elicitation of dermal sensitization in guinea pigs treated with TDI. Young adult guinea pigs received two open, epicutaneous induction applications (25 microliters) of 8,20, or 40% TDI in n-butyl ether on two separate areas. Five days later, animals were challenged with 0.0, 0.025, 0.05, 0.1, 0.2, and 0.4% TDI (25 microliter per concentration site). All challenge applications except the 0.0% solution elicited a positive response in 75 to 100% of the animals, and the severity of the skin reactions was dependent on the concentrations of the challenge and induction application. In another study at lower doses, animals received a total induction application (25 microliters per each of two sites) of either 4 or 8% TDI and were challenged with 0.0, 0.006, 0.012, 0.025, 0.05, and 0.1% of TDI (25 microliters per site). TDI did not elicit a sensitization response at challenge concentrations up to 0.012% (total application of 3 micrograms) when a 4% induction application was used, while a challenge concentration of 0.025% (total application of 6.25 micrograms) elicited a sensitization response in 63% of the animals. At the 8% induction application (total application of 4000 micrograms), all challenges, except the 0.0% indicated sensitization, and the intensities of the skin reactions were correlated with the challenge concentrations and the induction application. In conclusion, the results demonstrate that TDI produced sensitization at dilute induction concentrations and that the severity of the dermal response was correlated with the concentration used at induction and challenge. Furthermore, no observed effect levels were determined below which the challenge concentration did not elicit a dermal hypersensitivity reaction. When 4% TDI was applied at induction, no observed effect was seen with a dermal challenge application of 3 micrograms whereas an effect was seen with 6.25 micrograms (in 25 microliters) when n-butyl ether was the solvent.

Renal transport of NAP-taurine.

The renal transport of N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (NAP-taurine), a potential photoaffinity label, was studied using the rabbit renal cortical slice and the isolated perfused rat kidney. NAP-taurine inhibited the slice accumulation of PAH in a dose-dependent manner (ID50 = 2.5 X 10(-5) M). It accumulated to a steady-state slice-to-medium concentration ratio of 14. However, NAP-taurine was not toxic to the tissue, as it did not influence the accumulation of the organic cation tetraethylammonium. NAP-taurine transport was saturable and its accumulation was inhibited by the metabolic inhibitors PAH, probenecid, 4,4'-diisothiocyano-2,2'-disulfonic stilbene (DIDS), ouabain, and the absence of sodium. Kinetic studies showed that the Km for NAP-taurine is 3.5 X 10(-5) M, and also that PAH competitively inhibits NAP-taurine influx with a Ki of 1.2 X 10(-3) M. Experiments with the rat isolated perfused kidney gave the NAP-taurine-to-inulin clearance ratio of approximately 5, indicating net tubular secretion. DIDS significantly reduced this clearance ratio to 0.8. The results suggest NAP-taurine is handled by the kidney in a manner analogous to PAH and may thus be useful as a photoaffinity label for the renal organic anion transport system.

The effect of bis(p-chlorophenyl) acetic acid on the renal function of the rat.

The principle water-soluble metabolite of DDT in mammals has been shown to be DDA (bis(p-chlorophenyl)acetic acid). Previous studies suggested that DDA was secreted by the renal proximal tubule and was reabsorbed at an unspecified site in the nephron. Since DDA has been known to produce alterations in cellular functions, the present study examined the possibility that the renal transport of DDA was capable of causing acute nephrotoxicity. When 100 mg/kg of DDA was infused iv into the rat during a 90 min period, there was a significant decrease (congruent to 20%) in the glomerular filtration rate (GFR) after 110 min from the start of administration. During these experiments, there was no change in the mean arterial blood pressure (MABP), urine flow rate (V), renal clearance of tetraethylammonium (CTEA) or fractional reabsorption of Na (FRNa). After 200 mg/kg of DDA was infused iv into the rat during a 90 min period, there was a 60% decrease in the GFR, CTEA and V. However, the decrease in renal function was accompanied by a dramatic reduction in MABP (125 to 60 mmHg). To determine whether DDA could have produced acute renal failure when the perfusion pressure was kept constant, isolated kidney experiments were performed. In these experiments, DDA (1.0 mM) was present in a dextran perfusate and the perfusion pressure was kept constant at 90 mmHg. During these experiments, the GFR, V and FRNa were decreased significantly. The results indicated that a high perfusate concentration of DDA caused acute renal failure in the isolated kidney which was produced even when the perfusion pressure was kept constant. In conclusion, DDA produced renal failure in vivo which was associated with a reduction in renal perfusion pressure; however, perfused kidney experiments indicated that DDA could have caused a direct effect on nephron function.

Renal tubular transport and nephrotoxicity of DDA.

Since DDA [bis(p-chlorophenyl)acetic acid] has been shown to be transported and concentrated by the renal proximal tubule, this metabolite of DDT has been postulated to be a potential nephrotoxic agent. The present study explored the renal transport of DDA in the isolated, perfused rat kidney and the effects of DDA on renal function. When DDA (0.6 microM) was present in a dextran perfusate which eliminated DDA-colloid binding, the DDA/inulin clearance ratio was congruent to 0.05; however, some metabolism of DDA was apparent. During these studies, DDA had no effect on the glomerular filtration rate and the fractional reabsorption of Na, K or H2O. To determine the concentration of DDA which would produce an effect on renal cellular function, studies were performed with renal cortical slices. DDA at media concentrations greater than or equal to 0.1 mM were needed to produce significant alterations in tetraethylammonium transport, tissue oxygen consumption and intracellular electrolyte composition; however, no effect was demonstrated on Na-K-ATPase activity although DDA did affect Mg-ATPase activity. In conclusion, DDA at a 0.6 microM perfusate concentration undergoes net tubular reabsorption and metabolism without affecting the function of the perfused kidney. Only high concentrations of DDA were shown to produce alterations in cellular function.

Effects of SCN- and NO3- on organic anion transport in rabbit kidney cortical slices.

1. The effects of replacement of Cl- by either SCN- or NO3- on the accumulation of p-aminohippurate, the efflux of pre-accumulated p-amino-hippurate and kinetics of p-aminohippurate uptake were investigated in the rabbit kidney cortical slice. 2. The total replacement of Cl- in the incubation medium with SCN- decreased the 60-min slice-to-medium concentration ratio (S/M) of p-amino-hippurate by 75% and that with NO3- by 40%. 3. The decrease in p-aminohippurate accumulation by the inorganic ions was found to be specific for organic anion transport since the uptake of the organic cation, tetraethylammonium, was not influenced by inorganic ions. 4. The influence of NO3- on p-aminohippurate uptake was fully reversible: however, the effect of SCN- could only be partially reversed. 5. Both SCN- and NO3- significantly increased the Km value but had no significant effect on the V value of the p-aminohippurate uptake process. 6. These findings suggest that both SCN- and NO3- are competitive inhibitors of p-aminohippurate transport and, also, that SCN- appears to bind to a membrane component involved in the transport of p-aminohippurate.