Herbert H. Cornish

Biological responses of the rat to polychlorinated biphenyls

Abstract A commercial polychlorinated biphenyl mixture (PCBs), Aroclor 1242, was administered to rats po by intubation in order to determine toxic manifestations of acute and subacute ingestion. In addition, the effect of PCBs on hepatic microsomal enzyme systems in rats was evaluated. The oral, 14-day LD50 was determined to be approximately 4.25 g/kg. Major toxic signs observed upon administration of high doses of PCBs included diarrhea, chromodacryorrhea, loss of body weight, unusual stance and gait, lack of response to pain stimuli, and terminal ataxia. Progressive dehydration and CNS depression appeared to be contributing factors in each fatality. Histopathologic alterations were evident only in the liver and kidneys, manifest as foci of sudanophilic vacuolation. Rats maintained on an oral dosage regimen of 100 mg/kg every other day for 3 weeks exhibited similar histopathologic changes, but no overt signs of toxicity. Serum GOT activities were elevated over controls in both the acute and subacute groups. A single ip injection (100 mg/kg) increased liver weight, total hepatic microsomal enzyme activity (measured as hydroxylation of acetanilide and N-demethylation of aminopyrine), and hepatic cytochrome P 450 and b 5 levels. Hepatic microsomal enzyme activity remained elevated 10 days after a single dose of PCBs, suggesting that PCBs may play an important role in altering biologic responses of mammals subjected to environmental chemical stress.

Ethanol Potentiation of Halogenated Aliphatic Solvent Toxicity

Abstract This study was undertaken to determine the potentiating action of prior ethanol ingestion on the toxicity of carbon tetrachloride, trichloroethylene, perchloro-ethylene, and 1,1,1-trichloroethylene. Ethanol potentiation of toxicity, as measured by serum enzyme response, could be demonstrated only after exposure of rats to carbon tetrachloride or trichloroethylene.

Effect of pretreatment of rats with carbon tetrachloride on tolerance development.

Abstract To evaluate the effect of pretreatment of rats with CCl 4 on tolerance development to subsequent exposures, rats were exposed 25–7500 ppm of CCl 4 vapor or given CCl 4 orally, 3.25 mg/g body weight. Forty-eight hours later these rats were reexposed to a normally lethal 7500 ppm CCl 4 concentration. Mortality, blood clotting time, serum bilirubin, serum and liver triglycerides, and CCl 4 and CHCl 3 concentrations in tissues and in the whole rat were used as a measure of the response to CCl 4 exposure. Conversion of CCl 4 to CHCl 3 in vitro was also determined in normal and pretreated animals. It was found that animals exposed to 4000 ppm for 6 hr or given 3.25 mg/g of CCl 4 orally developed tolerance to subsequent normally lethal CCl 4 exposures. Serum bilirubin levels in animals protected by CCl 4 pretreatment were significantly lower than in those receiving only a single exposure to CCl 4 . Blood clotting times in protected animals were normal, while in those not protected by pretreatment, they were greatly prolonged. Serum triglyceride levels in protected animals were normal whereas they were considerably depressed in the nonprotected animals. Liver triglycerides were elevated in both protected and nonprotected, but were not as high in the protected animals. Carbon tetrachloride conversion to CHCl 3 was slower in protected than in the non-protected animals. Tolerance to CCl 4 developed in animals whose ability to metabolize CCl 4 had been depressed by pretreatment with the same compound. This suggests that the toxicity of CCl 4 is related to its metabolic pathway or to the production of toxic intermediates.

A Modified Spectrophotometric Method for the Determination of Hydrazine

Abstract The method is based on the reaction of p-dimethylaminobenzaldehyde with hydrazine and the formation of p-dimethylaminobenzaldazine, which, in the presence of strong acids, is rearranged into a p-quinoic chromophore structure. It was found that sufficient time must be allowed for the completion of aldazine formation and the most intensive color, proportional to the concentration of hydrazine, is developed in the presence of concentrated glacial acetic acid. The method is extremely sensitive and applicable to the determination of hydrazine in biological material.

Polychlorinated biphenyl-induced alteration of biologic parameters in the rat,

the Rat. BRUCKNER, J. V., KHANNA, K. L. AND CORNISH, H. H. (1974). Toxicol. Appl. Phurmacol. 2-8, 189-199, Aroclor 1242, a commercial polychlorinated biphenyl (PCB) mixture, was administered ip to rats for 10 weeks. Principal findings included: loss of body weight; hepatic and renal damage, with some animals exhibiting renal papillary epithelial hyperplasia; slight reduction in erythrocyte count, diameter, and hemoglobin content, with an elevation in serum iron; diminished plasma corticosteroid and glucose concentrations; increased urinary excretion of protein, sugars, and coproporphyrin. The effect of PCBs on several hepatic microsomal enzymatic parameters was also evaluated. Maximal hydroxylation and N-demethylation activities were observed 3-10 days following a single ip injection (100 mg/kg). Each remained significantly higher than control values after 20 days, with hydroxylation activity still 150 o/0 of controls after 40 days. The minimal effective single dose for induction of hydroxylation activity was approximately 5 mg/kg. Induction of hydroxylation activity was found to be dose-dependent; however, a smaller degree of correlation was noted between N-demethylation activity and dose. Values for cytochromes PbsO and b5 and NADPH-cytochrome c reductase activity were observed to roughly parallel hydroxylation and N-demethylation activities, the highest degree of correlation was manifest between enzymatic activity and cytochrome Pb5” values. Commercial polychlorinated biphenyl (PCB) products consist of mixtures of PCB isomers, differing from one another in extent of chlorination. Although their use has recently been voluntarily restricted in the United States to closed-system heat transfer applications, global environmental contamination and accumulation in food chains has been demonstrated (Risebrough and delappe, 1972). Humans have been exposed to PCBs, either via accidental contamination of foodstuffs by quantities large enough to elicit toxic symptoms (Kuratsune et al., 1972), or via PCB residues in everyday foods. The latter mode of exposure has apparently resulted in deposition of detectable concentrations (al ppm wet weight) of PCBs in human adipose tissue within the general population of the United States (Price and Welch, 1972).

Problems Posed By Observations Of Serum Enzyme Changes In Toxicology

(1971). Problems Posed By Observations Of Serum Enzyme Changes In Toxicology. CRC Critical Reviews in Toxicology: Vol. 1, No. 1, pp. 1-32.

Metabolism of caffeine-3H in the rat

The methodology for the unequivocal identification of caffeine and 13 possible metabolites (mono, di- and tri-N-methylated xanthine and uric acid derivatives) based on TLC, UV and mass spectrometry has been developed. Upon ip administration of caffeine-3H to the rat, 64–67% of the radioactivity was recovered in the urine over a period of 24 hr. The chloroform-methanol (9:1) extract of the urine accounted for about 37% of the administered radioactivity. Water soluble metabolites constitute approximately 30% of the injected caffeine-3H. With the aid of preparative TLC, 8.8% of unchanged caffeine and the following metabolites were isolated from chloroform-methanol extract of urine: theophylline (1.2%), theobromine (5.1%), paraxanthine (8.8%) and trace amounts of 1,3,7-trimethyluric acid and 3-methyluric acid. Two unidentified metabolites (metabolite A, 11.4% and metabolite B, 1.3%) have also been isolated.

Correlation between serum enzymes, isozyme patterns and histologically detectable organ damage☆

Abstract Serum enzyme levels and isozyme profile were utilized as a measure of hepatotoxic response to carbon tetrachloride, mercuric chloride, diethanolamine and thioacetamide. The sensitivity of these measurements was compared with the degree of morphological damage to the liver or kidney as assessed by light and electron microscopy. Morphological damage was present at dosage levels considerably below those necessary to induce detectable enzyme alterations. Generally, advanced degenerative change, including necrosis, had occurred in both the liver and kidney before enzyme alterations were seen.

Effects of lead on the induction of hepatic microsomal enzymes by phenobarbital and 3,4-benzpyrene☆☆☆

Abstract A single ip injection of lead acetate (65 mg/kg) prolonged the duration of zoxazolamine paralysis in Sprague-Dawley rats and prevented the stimulation of zoxazolamine metabolism normally induced by phenobarbital. Lead also delayed the phenobarbital induction of hepatic microsomal cytochrome P -450 at 12 and 24 hr after treatment. However, the inhibitory effect of lead had disappeared and cytochrome P -450 concentrations were markedly elevated at 48 hr. Lead also diminished hepatic microsomal cytochrome P -448, normally resulting from benzyprene treatment. Neither lead, phenobarbital, benzyprene nor their combination had a significant effect on hepatic cytochrome b 5 values. Lead, in vitro , inhibited the hepatic microsomal NADPH-cytochrome c and P -450 reductase activity in a dose-dependent manner. In vivo , significant inhibition of NADPH-cytochrome c and P -450 reductase activity was observed after the injection of lead acetate. Significant inhibition coincides with the time when lead concentration in the hepatic microsomes was maximal. The inhibition of δ-aminolevulinic acid dehydratase (ALAD) activity at several blood lead concentrations was confirmed both in vivo and in vitro . This relationship between blood lead concentrations and ALAD activity was not altered by pretreatment with phenobarbital or benzpyrene.

THE ROLE OF VITAMIN B6 IN THE TOXICITY OF HYDRAZINES

Within recent years hydrazine and the methyl substituted hydrazines have come into considerable use as rocket fuels. As a result of this increased production of hydrazines, the possibility of accidental human exposure is of considerable interest. Obvious concern results from the fact that hydrazine had been used as an experimental means of producing fatty liver in experimental animals for many years. On an acute toxicity basis, O’Brien and coworkers (1964) reported comparative lethal dosebo ( LDSo) values for hydrazine 64 mg/ kg ( 2 mmoles/kg) , rnonomethylhydrazine (MMH) 28 mg/kg (0.61 mmoles/ kg), 1,l-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) 102 mg/kg ( 1.7 mmoles/ kg) , and 1 ,Zdimethylhydrazine (symmetrical dimethylhydrazine, SDMH) essentially nontoxic even at dosages of 500 mg/kg. The structures of these four compounds are shown in FIGURE 1, and it appears that a free amino group is essential for biological activity in this group of compounds. Barth and associates ( 1967) have previously reported the diuretic effect induced by UDMH, and it is interesting to note that of the four hydrazines shown in FIGURE 1, only SDMH is without diuretic effect, again emphasizing the biological activity of the free amino groups in this series of compounds. Killam and Bain reported in 1957 that thiosemicarbazide, furoyl hydrazide, and isonicotinic acid hydrazide would inhibit, in vitro, enzyme systems catalyzed by vitamin Bg. Thus it was suggested that the epileptiform convulsions produced by these compounds could be due to an inhibition of one or more of the enzyme systems requiring pyridoxal phosphate as a cofactor. In related findings, Reeves (1961 ) and Back and colleagues (1963) reported the use of pyridoxine and pyridoxamine as effective antidotes for UDMH and MMH toxicity. Similar findings on the effectiveness of pyridoxine in alleviating the convulsive symptoms of hydrazine toxicity have not been consistent. Medina ( 1963) reported that convulsions induced by hydrazine could be blocked by pyridoxine, but not by pyridoxal. O’Brien and associates (1964) reported that although hydrazine can be a convulsant at high doses, at doses near the LDJO it is not primarily a convulsant but is a depressant. On this basis, they suggest that hydrazine probably has a mode of action different from UDMH and MMH. It is interesting to note that this suggestion correlates with the early reports that brain levels of y-amino-butyric acid (GABA) are depressed after UDMH treatment but apparently elevated after hydrazine treatment.