Donald N. McMartin

Effect of age on axoplasmic transport of cholinesterase in rat sciatic nerves

Senile muscle atrophy has been attributed to an impaired ability of old nerves to transport trophic factors. To evaluate the effect of age on axoplasmic transport, we measured the accumulation of cholinesterase activity above a ligature around sciatic nerves of young (7--8 months), middle-aged (19--20 months), and old (31--32 months) male rats. Protein content and cholinesterase activity per mm of nerve were higher in middle-aged and old than in young nerves. However, accumulation of cholinesterase activity was significantly lower by middle age and was strikingly reduced by old age. This large reduction in axoplasmic transport appeared to result from factors other than axonal loss. A model in which old nerves have an increased number of temporary focal blockages of particle movement in axoplasmic channels is proposed to explain the decreased transport.

Influence of aging and induction on rat liver and kidney microsomal mixed function oxidase systems

Abstract In an effort to investigate the diminished capacity of old individuals to metabolize certain drugs we studied the effect of old age on the concentrations and inductibility of the hepatic and renal mixed function oxidase systems of rats. One group of rats (4, 12, and 36 months old) were induced with phenobarbital (PB) and another group (7 and 31 months old) with β-naphthoflavone (BNF). Cytochrome P -450, cytochrome b 5 , and NADPH-cytochrome P -450 reductase concentrations were determined in control and PB-induced liver or BNF-induced liver and kidney microsomes. In vivo rates of R -warfarin metabolism catalyzed by liver and kidney microsomes were used as a probe of the forms of cytochrome P -450 present. Livers and kidneys were judged to be free of significant histologic lesions. Hepatic and renal cytochrome P -450 and cytochrome b 5 concentrations were increased by BNF induction while PB induction increased hepatic cytochrome P -450 and did not affect cytochrome b 5 . Hepatic NADPH-cytochrome P -450 reductase activities were increased by PB induction and decreased by BNF induction while activity of the renal enzyme was increased by BNF induction. Cytochrome P -450 concentrations were lower in old control and induced livers and kidneys. Aging also decreased concentrations of renal cytochrome b 5 and NADPH-cytochrome P -450 reductase. The inducibility of hepatic cytochrome P -450 by PB was also diminished in old rats. From the results of aging on R -warfarin metabolite patterns it was determined that the activity of the major form of cytochrome P -450, BNF-B in BNF-induced rats was unaltered in the livers and significantly diminished in the kidneys of old rats. Two forms of cytochrome P -450 in PB-induced rats, PB-C and PB-B, demonstrated diminished ability to be induced and PB-C showed diminished activity in old rats.

Induction of hepatic microsomal cytochrome P-450 by mirex and Kepone☆☆☆

Abstract The chlorinated insecticides, mirex and Kepone, pose a threat to human health as a consequence of their pollution of the environment. We investigated their potential to affect synergistically the toxicity of other xenobiotics and the pharmacological function of drugs by induction of hepatic microsomal enzymes. Male rats were induced by ip injection of mirex (50 or 5 mg/kg/day for 5 days) or Kepone (10 or 1 mg/kg/day for 5 days). Metabolic activity was tested with warfarin and biphenyl using high-performance liquid chromatographic assays. The high doses of both compounds induced cytochrome P-450 with absorbance bands (reduced, CO complex) at 449 nm. Cytochrome concentrations were enhanced twofold relative to controls. Mirex resembled 3-methylcholanthrene and benzo[a]pyrene by inducing formation of 6-hydroxywarfarin but differed in not inducing 8-hydroxywarfarin. Kepone resembled phenobarbital in inducing 7-hydroxywarfarin but differed in its effects on the other metabolites. The low dose of mirex induced higher amounts of 4′-hydroxywarfarin than did the high dose. The metabolite profiles with high and low doses of Kepone also showed marked variations from one another. Mirex and Kepone are carcinogenic in rats and mice but, in contrast to the polycyclic aromatic carcinogens, do not markedly enhance the activity of microsomal biphenyl 2-hydroxylase relative to biphenyl 4-hydroxylase. We conclude that mirex and Kepone induce hepatic mixed-function oxidase profiles which differ from one another and from the classical inducers, phenobarbital and 3-methylcholanthrene. Mirex apparently only induces one of the enzymes induced by 3-methylcholanthrene. The enzyme profiles arising from the insecticides are dose dependent and will thus potentiate qualitatively differing effects depending on the level of ingestion.

Acute toxicity in guinea pigs and rabbits of soot from a polychlorinated biphenyl-containing transformer fire

Abstract A fire involving a polychlorinated biphenyl (PCB)-containing transformer extensively contaminated the State Office Building in Binghamton, New York, with a sootlike material containing 2,3,7,8-tetrachlorodibenzo- p -dioxin (2,3,7,8-TCDD), 2,3,7,8-tetrachlorodibenzofuran, and high concentrations of numerous other polychlorinated dibenzodioxins, dibenzofurans, and PCBs. The oral LD50s of the soot and of its benzene extract, each administered to female guinea pigs in 0.75% aqueous methyl cellulose, were 410 mg of soot/kg and 327 mg of soot equivalent/kg, respectively. Serum triglycerides were elevated in males at 100 and 500 mg/kg and in females at 500 mg/kg. Alkaline phosphatase was lowered in females at 500 mg/kg. Histopathology revealed dose-related pancreatic duct hyperplasia and salivary gland duct metaplasia in males. Body weight loss was observed in both sexes at 500 mg/kg. Thymus weight decreased in both sexes at 100 and 500 mg/kg, and kidney weights decreased in males at these doses. Dermal application of soot to rabbits for 24 hr caused no overt toxicity, although hepatic centrilobular hypertrophy was observed in both sexes. Similar application of soot extract caused a local serous inflammation in addition to the hepatic centrilobular hypertrophy. The oral LD50 for 2,3,7,8-TCDD in female guinea pigs was 19 μg/kg in aqueous methyl cellulose and 2.5 μg/kg in corn oil. We concluded that the soot matrix alters the dermal but not the oral toxicity of its components, that the toxic effects were consistent with those reported after exposure to dibenzodioxins and dibenzofurans, and the aqueous vehicle markedly diminished the acute toxicity of 2,3,7,8-TCDD relative to that in corn oil vehicle.

Lifetime toxicity of chloroform and bromodichloromethane when administered over a lifetime in rats

Chloroform (CHCl3) and bromodichloromethane (CHBrCl2) are the two most common haloorganic contaminants of chlorinated drinking water. A significantly increased incidence of hepatic neoplastic nodules was found in female rats when each of these compounds was administered in drinking water to Wistar rats throughout their life span. Hepatic adenofibrosis was also produced by chronic ingestion of these two halomethanes.

The role of cytochrome P-450-inducing agents in potentiating the toxicity of fluroxene (2,2,2-trifluoroethyl vinyl ether)

Abstract The effects of the hepatic microsomal cytochrome P -450-inducing agents 3-methylcholanthrene (MC), benzo[α]pyrene (BP), β-naphthoflavone (BNF), mirex, 8-hydromirex, Kepone, spironolactone, pregnenolone-16α-carbonitrile (PCN), barbital, phenobarbital (PB), mephobarbital, hexobarbital, and pentobarbital in potentiating the toxicity of the anesthetic fluroxene (2,2,2-trifluoroethyl vinyl ether) in male rats have been investigated. The toxicity was expressed as death, hepatic necrosis, or destruction of hepatic cytochrome P -450. Only PCN, mephobarbital, and phenobarbital induction caused death within 48 hr of the administration of fluroxene (2.5 g/kg, ip), and this was prevented by administration of cytochrome P -450 inhibitors. With PB induction the percentage of mortality correlated with the induced cytochrome P -450 concentrations. Fluroxene destroyed microsomal cytochrome P -450 in vivo , within 90 min of administration, and this destruction was enhanced over twofold by pretreatment of the rats with MC, BP, and all the barbiturates, and less significantly with BNF, Kepone, and PCN. Only the livers of mirex-, 8-hydromirex-, or MC-induced rats showed necrosis within 48 hr of administration of fluroxene, with 8-hydromirex-induced livers showing the most widespread necrosis. We conclude that a number of different forms of cytochrome P -450 can metabolize fluroxene to toxic products. Some forms of cytochrome P -450, particularly cytochrome P -448, are highly susceptible to destruction by fluroxene metabolites which probably arise from metabolism of the fluroxene vinyl group. Fluroxene-induced liver necrosis is not related to the destruction of cytochrome P -450, nor to the death of the experimental animals. Thus, the three aspects of fluroxene toxicity—mortality, cytochrome P -450 destruction and hepatic necrosis—are differentially affected.

Subchronic exposure of mice to Love Canal soil contaminants.

The health hazard potential of soil collected from the surface of the Love Canal chemical dump site in Niagara Falls, New York, was assessed in 90-day exposure studies. Female CD-1 mice were exposed to two concentrations of the volatile components of 1 kg of soil with and without direct soil contact. Control mice were identically housed but without soil. The soil was replaced weekly and 87 compounds were detected in the air in the cages above fresh and 7-day-old soil as analyzed by gas chromatography/mass spectrometry. The concentration of many of these compounds decreased during the 7-day exposure cycle. Histopathologic, hematologic, and serum enzyme studies followed necropsy of all mice. There was no mortality of mice exposed for up to 90 days under any condition. Thymus and spleen weights relative to body weight were increased after 4 weeks of exposure by inhalation but not after 8 or 12 weeks of exposure. alpha-, beta-, and delta- Benzenehexachlorides , pentachlorobenzene, and hexachlorobenzene were detected in liver tissue from these animals. Mice exposed to 5- to 10-fold elevated concentration of volatiles had increased body and relative kidney weights. There was no chemically induced lesion in any animal exposed only to the volatile soil contaminants. Mice exposed by direct contact with the soil without elevated volatile exposure had increased body (10%) and relative liver weights (169%). Centrolobular hepatocyte hypertrophy, which involved 40 to 70% of the lobules, was observed in all mice in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of fluroxene (2,2,2-trifluoroethyl vinyl ether) toxicity with polychlorinated biphenyls.

The effects of induction of rat hepatic microsomal cytochrome P-450 by commercial mixtures of polychlorinated biphenyls (PCBs) (100 mg/kg/day for 3 days) in potentiating the toxicity of the anesthetic fluroxene (2,2,2-trifluoroethyl vinyl ether) have been determined. The PCB mixtures used were Aroclors 1221, 1016, 1254, and 1260. All Aroclors significantly induced cytochrome P-450 relative to controls (1.4–2.1), and the more highly chlorinated PCB mixtures produced the greatest induction. The cytochrome P-450 composition of the Aroclor-induced microsomes was probed using R warfarin metabolism. Aroclor 1254-induced microsomes comprised mainly cytochrome P-448 of the 3-methylcholanthrene-inducible type, and Aroclor 1260-induced microsomes comprised mainly cytochrome P-450 of the phenobarbital-inducible type, although each contained lesser quantities of the other forms. Only Aroclor 1254 and 1260 induction produced death in rats (12/20 and 11/13 respectively) following ip administration of fluroxene (2.5 g/kg body wt). Fluroxene potentiated the destruction of cytochrome P-450 in vivo and this destruction was enhanced by Aroclor induction. Cytochrome P-448 suffered the greatest destruction in Aroclor 1221- and 1254-induced microsomes, and cytochrome P-450 was most extensively destroyed in Aroclor 1260-induced microsomes. The Aroclor 1254-induced cytochrome P-450 concentration did not return to the corresponding control value 24 hr after clearance of the fluroxene dose which implies that fluroxene metabolism interferes with the biosynthesis of cytochrome P-450. It is concluded that some Aroclors, through induction of cytochrome P-450 of the phenobarbital-inducible type, increase the rates of metabolism of fluroxene, which results in the production of toxic metabolites leading to liver necrosis, destruction of cytochrome P-450, and death.

Subchronic oral toxicity in guinea pigs of soot from a polychlorinated biphenyl-containing transformer fire

We have previously described the acute po toxicity in guinea pigs of soot from a transformer fire at the State Office Building in Binghamton, New York. The soot was determined to contain polychlorinated biphenyls, biphenylenes, dibenzodioxins, and dibenzofurans. The present study evaluates soot toxicity in guinea pigs receiving 0, 0.2, 1.9, 9.3, or 46.3 ppm soot in the feed for 90 days or 231.5 ppm for 32 days. At 231.5 ppm, body weight loss, thymic atrophy, bone marrow depletion, skeletal muscle and gastrointestinal tract epithelial degeneration, and fatty infiltration of hepatocytes were observed. Mortality had reached 35% by Day 32 (when survivors were killed), with total soot consumption of approximately 400 mg/kg. At 46.3 or 9.3 ppm soot, a reduced rate of body weight gain was observed, and at 46.3 ppm, the mortality by Day 90 was 30%. Relative (to body) thymus weights were decreased in both groups, while relative spleen weights were increased at 46.3 ppm soot only. Salivary gland interlobular duct squamous metaplasia and focal lacrimal gland adenitis were detected histopathologically, while bone marrow depletion was noted only in females at the higher dose. Diminished serum alanine aminotransferase (ALT) activity in both sexes and decreased serum sodium levels in male and potassium levels in female animals were detected at both dose levels. decreased gamma-glutamyl transferase activity and red blood cell count and elevated serum creatinine and triglycerides were observed only in animals fed 46.3 ppm soot. At 1.9 ppm soot, salivary gland duct metaplasia was observed in both sexes, along with decreased relative thymus weights, ALT activity, and serum sodium levels in male animals only. No effects attributable to soot exposure were noted in animals receiving 0.2 ppm soot for 90 days. Total average soot consumption for male and female animals in the 0.2, 1.9, 9.3, and 46.3 ppm dosage groups was 1.2, 12, 55, and 275 mg/kg, respectively. Although many of the observed effects were typical of acute exposure of guinea pigs to the Binghamton soot or to polychlorinated aromatic hydrocarbons in general, salivary gland duct metaplasia has not been previously reported. Toxic effects of this subchronic exposure were observed at lower total doses than with acute exposure, although variations in absorption due to the effects of different vehicles (aqueous in the acute study versus the feed in this study) could account for some or all of this difference.

Trifluorinated ether anesthetic lethality in rats: The role of bacterial infection☆

The lethal effects of the fluorinated ether anesthetics fluroxene (2,2,2-trifluoroethyl vinyl ether) and its ethyl (TFEE) and allyl analogues in male Wistar rats have previously been demonstrated to be potentiated by specific hepatic microsomal cytochromes P-450, and mediated by the common metabolite 2,2,2-trifluoroethanol (TFE). We report here that administration of lethal combinations of anesthetic and cytochrome P-450-inducing agents or of lethal doses of TFE (0.21 g/kg and higher) to rats caused decreased white blood cell counts, necrosis of sternum bone marrow cells and lymphocytes in the thymic cortex, and resulted in Escherichia coli contamination of the blood, lungs, liver, and kidneys of treated rats. Control animals in identical environments were free of bacterial contamination. Pretreatment of rats with the antibiotic tetracycline-HCl in the drinking water (0.6 g/liter) from 24 hr before anesthetic or TFE administration significantly diminished the mortality. With TFEE and beta-naphthoflavone induction, mortality was reduced from 85 to 30% by the antibiotic. However, the antibody plaque assay following immunization with sheep erythrocytes indicated that the primary humoral immune response to a thymus-dependent antigen was not impaired in treated rats. These results considered together indicate that metabolic formation of TFE from the anesthetic agents produced a decreased host resistance with subsequent increased susceptibility to bacterial infection. If not administered the antibiotic, the animals succumbed to the infection.