P.P. Sapienza

Distribution of bisphenol A in the neuroendocrine organs of female rats

The distribution of 14C-bisphenol A (BPA) in plasma and neuroendocrine organs was determined in Fischer 344 female rats following three oral doses (0.1, 10 or 100 mg/kg). Plasma and tissue maximum concentrations (Cmax) were reached within 15-30 min of dosing. Plasma areas-under-the-curve (AUC) ranged from 0.06 to 53.9 mg-h/mL. The AUCs of the pituitary gland and uterus/gonads were 16-21% higher than that of plasma. The AUCs of hypothalamus and the rest of the brain were 43.7% and 77% of the plasma AUCs, respectively. In the brain tissue, the exposure increased linearly with the oral dose, as the dose was increased from 0.1 to 10 and 100 mg/kg; the exposure in the brain relative to the plasma increased by factors of 1, 1.19 and 1.24. This indicates that the brain barrier systems do not limit the access of the lipophilic BPA to the brain. The increases of the uterus/gonads relative to the plasma were 1, 1.07 and 1.04. Tissue partitioning was also examined in vitro by the uptake of 14C-BPA. The BPA tissue/blood partition coefficients were as follows: heart, 7.5; liver, 6.1; kidney, 6.4; fat, 3.6; muscle, 2.6; breast, 3.6; ovaries, 9.1; uterus, 5.9; stomach, 5.1; and small intestine, 6.7. The tissue/cerebrospinal fluid partition coefficients were as follows: pituitary gland, 12.8; brain stem, 6.1; cerebellum, 6.4; hippocampus, 7.1; hypothalamus, 6.1; frontal cortex, 4.9; and caudate nucleus, 6.8.

Effects of the seafood toxin domoic acid on glutamate uptake by rat astrocytes.

Pronounced glutamic acid uptake was observed after only 15 min with glutamate concentrations of 60 nmol/mg protein when astrocytes were incubated with 1 mM glutamic acid. The uptake increased with time to a steady-state glutamate level of above 160 nmol/mg protein by 45 min. The uptake was energy dependent. Reduced temperature (0 degrees C) and ouabain (100 microM) inhibited uptake by 86.7% (P<0.001; n=18) and 84.4% (P<0.001; n=18), respectively, when compared with controls. After exposure of astrocytes to glutamate (1 mM) in the incubation medium, in the presence of domoic acid (10 and 100 microM) at 5 and 60 min, domoic acid (10 microM) elevated glutamate uptake by 64.0% (P<0.05; n=34) at 5 min but decreased glutamate uptake by 47.8% (P<0.01; n=19) at 60 min compared with controls. A higher dose of domoic acid (100 microM) decreased glutamate uptake by 49.6% (P<0.01; n=20) and 61.3% (P<0.001; n=20) at 5 and 60 min, respectively, compared with controls. This study suggests that domoic acid may induce neurotoxicity because of the failure of astrocytes to remove extracellular glutamate. This may contribute to excitotoxic injury.

Protective Effect of l‐Carnitine in the Neurotoxicity Induced by the Mitochondrial Inhibitor 3‐Nitropropionic Acid (3‐NPA)

ZBIGNIEW BINIENDA,a,c JOHN R. JOHNSON,a ALEXANDER A. TYLER-HASHEMI,a ROBERT L. ROUNTREE,a PHILIP P. SAPIENZA,b SYED F. ALI,a AND CHUNG S. KIMb aDivision of Neurotoxicology, National Center for Toxicological Research/ Food and Drug Administration (NCTR/FDA), Jefferson, Arkansas, USA bDivision of Toxicological Research, Center for Food Safety and Applied Nutrition/ Food and Drug Administration (CFSAN/FDA), Washington, DC, USA

Distribution, metabolism and excretion of pentachloroanisole in the beagle dog and miniature pig

Tissue distribution, excretion and metabolism studies of pentachloroanisole (PCA), an environmental metabolite of pentachlorophenol (PCP), were conducted in the beagle dog and miniature pig following single oral doses (25 mg/kg) of radiolabelled PCA. PCA was readily demethylated by both species, with a half-life of 5-8 min. The resultant PCP was the major metabolite in dogs and pigs. In the dog, an average of 21.9% of the administered radiolabel was excreted in the urine and 62.3% in the faeces during a 7-day period. Of the tissues analysed, an average of 3.2% of the radiolabel remained in the liver, and blood and muscle accounted for averages of 3.0 and 2.3%, respectively, of the dose. Free and conjugated PCP were found in the urine of dogs; no PCA or tetrachlorohydroquinone (TCH) were found. In dog faeces, PCP and a trace of polar material were observed; no PCA was excreted in dog faeces. In the miniature pig, an average of 25.8% of the administered radiolabel was excreted in the urine and 32.0% in the faeces during a 2-wk period. An average of 4.4% of the radiolabel was found in the liver, 8.8% in the blood, 7.1% in the muscle and 6.4% in the fat. In pig urine, PCP and conjugated PCP were the only metabolites observed; no PCA or TCH was found. Pig faeces contained a trace of unchanged PCA; PCP and polar metabolites were also found. Since pig tissues retained a sizeable residue 2 wk after a single dose of PCA, various agents were used in an attempt to decrease the tissue level of radiolabel in pigs; anion exchange resin was found to be the most effective.

Distribution and excretion of radiolabelled tert-butylhydroquinone in Fischer 344 rats

Uniformly 14C-ring-labelled tert-butylhydroquinone (TBHQ) was diluted with non-radioactive TBHQ and administered orally (for excretion studies) to Fischer 344 rats. An average of 72.9% and 10.6% of the administered radioactivity was recovered in the urine and faeces, respectively, of male rats, and 77.3% and 8.2% in the urine and faeces, respectively, of female rats in 4 days. No significant sex-related differences were found in either excretion, tissue distribution or urinary metabolites of TBHQ-derived radiolabel. For distribution studies, intraperitoneal doses were administered to female rats, and tissue levels of radiolabel were determined at various times after dosing. The parent compound quickly disappeared from tissue in vivo. The highest concentrations of radiolabel were found in the liver and kidneys. The urinary metabolites consisted of conjugated TBHQ and unidentified polar substance(s).

Disposition and metabolism of radiolabelled pentachloroanisole in rats and rabbits

Male Sprague-Dawley rats and New Zealand White rabbits were administered 14C-labelled pentachloroanisole (PCA) in corn oil by gavage as single doses of 25 mg/kg and were then placed in individual metabolism cages for as long as 4 days. Peak blood level of radioactivity occurred 6 hr after administration of the dose to rats and between 3 and 4 hr in rabbits; the blood elimination half-life ranged from 8 to 15 hr in rats and averaged 6 hr in rabbits. Rats excreted an average of 54.2% of the administered radiolabel in the urine and 32.4% in the faeces during the 96 hr following the dose; rabbits excreted an average of 84.2 and 13.1% of the radiolabel in the urine and faeces, respectively, during this time. Examination of the metabolites in the rat showed that 60% of the urinary radioactivity was attributable to tetrachlorohydroquinone (TCH), 3% to free pentachlorophenol (PCP) and 29% to conjugated PCP; faecal metabolites were PCP (85.7%), TCH (4.3%) and polar metabolite(s) (10%). In the rabbit, 58% of the urinary radioactivity was attributable to TCH, 8% to free PCP and 34% to conjugated PCP. Faecal metabolites consisted of PCP and conjugated material.

Excretion and tissue distribution of 14C-labelled 8-methoxypsoralen in Beagle dogs and miniature pigs.

Male beagle dogs and miniature swine were given 14C-labelled 8-methoxypsoralen (8-MOP) as a single oral dose (10 mg/kg body weight). In dogs, there appeared to be wide variability in 8-MOP absorption as indicated by the broad range of percentages of radioactivity recovered from urine and faeces over a 4-day period (3.6-24.7% in urine; 47.3-94.9% in faeces); mean recovery values were 13.6% in the urine and 68.6% in the faeces. In pigs, considerable variability in absorption was also evident, but not to the extent of that seen in dogs. Based on the fraction of the dose recovered in the urine, the absorption of 8-MOP was greater in pigs; the proportion of the dose recovered in urine over a 7-day period ranged from 25.8 to 57.8%. Faecal recovery ranged from 15.4 to 49.0% of the dose. Mean recovery values in pigs were 45.4% in urine and 35.6% in faeces. Most of the 8-MOP was cleared from the bodies of dogs and pigs in a few days, and little 8-MOP residue was sequestered in any of the tissues examined in either species. Small amounts of an 8-MOP-related substance remained in the liver and blood for as long as 4 days in dogs and 7 days in pigs.

Distribution and pharmacokinetics of double-radiolabeled endotoxin in the rat brain and peripheral organs

The endotoxin, lipopolysaccharide (LPS), of Salmonella typhimurium was biosynthetically labeled with 3H and 14C incorporated into the fatty acyl chains and glucosamine residues, respectively. The radio-labeled LPS was isolated from the bacteria and then injected into Sprague-Dawley rats. The distribution of 14C and 3H-LPS in plasma and other organs was determined following intraperitoneal (IP) doses of 14C and 3H-LPS (200 μg/kg). Plasma concentrations of both fatty acyl chains and glucosamine residues were biphasic, with a relatively rapid decay followed by a slow decline for 48 h. Similar biphasic results were found in the peripheral organs (kidney and heart) and brain barrier tissues (meninges and choroid plexus). In other brain tissues (brain stem, caudate nucleus, hypothalamus, frontal cortex, cerebellum and hippocampus), the glucosamine residue was biphasic, whereas the fatty acyl chains showed accumulation. Highest concentrations of LPS were found in the plasma, spleen and the liver. In addition, in the liver, sustained elevations of 14C-glucosamine and 3H-fatty acyl chains were observed. This indicates LPS accumulation in the liver. By contrast, the spleen showed biphasic decay of glucosamine residues and accumulation of fatty acyl chains. In the brain barrier tissues, peak LPS concentrations were significantly reduced (about 70%) and were further reduced (about 95%) in other brain tissues. The high elevation of LPS in the spleen is considered indicative of an immune response. Our findings highlight the potential significant role of lipid A as shown with the sustained elevation of 3H-fatty acyl chains in the brain.

Distribution of androstenedione and its effects on total free fatty acids in pregnant rats

Androstenedione, an anabolic steroid used to enhance athletic performance, was administered in corn oil by gastric intubation once daily in the morning to nonpregnant female rats at a dose of 5 or 60mg/kg/day, beginning two weeks before mating and continuing through gestation day (GD) 19. On GD 20, the distribution of androstenedione and other steroid metabolites was investigated in the maternal plasma and target organs, including brain and liver. The concentration of estradiol in plasma approached a statistically significant increase after treatment as compared with the controls, whereas the levels of androstenedione, testosterone and progesterone were not significantly different from the controls. In the liver, the concentrations of androstenedione and estradiol only were increased in a dose-related manner. None of these steroids was detectable in the brain. Androstenedione treatment also produced changes in the level of selected free fatty acids (FFAs) in the maternal blood, brain, liver and fetal brain. The concentrations of palmitic acid (16:0) and stearic acid (18:0) in the plasma were not significantly different between the controls and treated rats. However, oleic acid (18:1), linoleic acid (18:2) and docosahexaenoic acid (DHA, 22:6) were 17.94 ± 2.06 μg/ml, 24.23 ± 2.42 μg/ml and 4.08 ± 0.53 μg/ml, respectively, in the controls, and none of these fatty acids was detectable in the treated plasma. On the other hand, palmitic, stearic, oleic, linoleic and DHA were present in both control and treated livers. Among the FFAs in liver, linoleic and DHA were increased 87% and 169%, respectively, over controls. Palmitic, stearic and oleic acids were not significantly affected by the 60 mg/kg treatment. These were present in both control maternal and fetal brains, whereas linoleic acid was found only in fetal brain control. DHA was present only in the control maternal brain (0.02 ± 0.02 μg/mg protein) and fetal brain (0.24 ± 0.15 μg/mg protein). The results indicated that androstenedione exhibits significantly different effects on the FFA composition among target organs during pregnancy.