A. W. Hayes

Teratogenicity of secalonic acid d in mice

Teratogenicity and fetotoxicity of secalonic acid D, a toxic fungal metabolite produced by Penicillium oxalicum, were investigated with pregnant CD1 mice. The compound was administered ip on d 7-15 of pregnancy. A dose-dependent reduction in weight gain of mothers receiving all doses of secalonic acid D and an increase in resorptions of implanted embryos of dams treated with more than 5 mg/kg secalonic acid D occurred. The latter effect was nearly 100% at 15 or 9 mg/kg given in NaHCO3 with or without dimethyl sulfoxide (DMSO), respectively. A corresponding decrease in the percent of live fetuses and a decrease in the average fetal body weight on d 19 of pregnancy also occurred. Multiple gross, skeletal, and visceral anomalies were noted in fetuses born to mothers receiving 10 mg/kg or more in NaHCO3 containing DMSO. In NaHCO3 alone, the minimum teratogenic dose was 6 mg/kg. Major malformations included cleft palate, cleft lip, open eyelids, missing phalangeal ossification centers, and shortened mandibles. The results indicated that secalonic acid D is embryocidal and teratogenic as well as fetotoxic when given to female CD1 mice during pregnancy.

Effects of the aflatoxins on ATPase activities in mouse and rat liver.

The effects of the aflatoxins on ATPase activities in mouse and rat tissues were investigated in vitro. The hepatic oligomycin-sensitive (O.S.) Mg++ ATPase was inhibited significantly. The order of inhibition was G1 greater than B1 greater than G2 greater than B2. Mouse O.S. Mg++ ATPase was more sensitive than the corresponding rat enzyme. The oligomycin-insensitive (O.I.) Mg++ ATPase activities in rat and mouse liver were not altered. Although aflatoxins G1 and B1 were more potent inhibitors of hepatic O.S. Mg++ ATPase, no concentration-response was observed, whereas aflatoxins G2 and B2 inhibited enzyme activity in a concentration-dependent manner. Spectral analysis of aflatoxin G1 solutions suggested that solubility was not related to the observed effects. In addition, the effects of aflatoxin B1 and G1 on mouse brain microsomal Na+-K+ ATPase were examined. Although aflatoxin B1 was more potent that G1, both mycotoxins significantly inhibited enzyme activity in a concentration-dependent fashion.

Conversion of rubratoxin B to the carboxylic acid derivative and its effect on adenosine triphosphatase activity and toxicity to mice.

Abstract The rate of conversion of rubratoxin B to its carboxylic acid derivative upon exposure to aqueous solvents was exponentially related to the relative abundance of water molecules. The same relationship existed for the rate of decrease in inhibition of Na+-K+ adenosine triphosphatase (ATPase) activity by rubratoxin B, when the toxin was incubated in the reaction mixture prior to addition of the enzyme. Inhibition of this enzyme activity by rubratoxin B was dose-dependent, with an IC50 of 5·8 x 10-6m, while the carboxylic acid derivative was much less effective, the IC50 being 19·3 x 10-6m. In mice, the ip LD50 of the carboxylic acid derivative dissolved in propylene glycol was more than twice that of the parent compound 24 hr after dosing, but beyond 24 hr there was little difference between the two values.

In vitro metabolism of [14C]rubratoxin B by rat hepatic subcellular fractions

Abstract The metabolism of rubratoxin B was studied in vitro using rat hepatic subcellular fractions. Primarily, metabolism of rubratoxin B involved a non-enzymatic process in the microsomal supernatant fluid. The transformation products were mainly water-soluble, although at least four unidentified organosoluble derivatives of rubratoxin B were detected. Three of these organosoluble derivatives were produced in the microsomal supernatant fluid by an enzymatic process.

Acute toxicity of patulin and its interaction with penicillic acid in dogs

Abstract The acute toxicity of iv-administered patulin and its interaction with ip-injected penicillic acid were investigated in male dogs. The LD 50 of patulin was estimated to be 10·4 mg/kg (95% confidence limits 7·2–15·1 mg/kg). Patulin had severe effects in dogs, particularly on the lungs. Lethargy, anorexia, haematemesis, diarrhoea, pulmonary haemorrhages and oedema, and luminal haemorrhages of the gastro-intestinal tract were common features in dogs given patulin in a dose of 10 mg/kg or more. Sublethal doses (7·5 mg/kg or less) did not have drastic pulmonary effects. Enhancement of patulin toxicity by penicillic acid was indicated by the occurrence of deaths in dogs exposed simultaneously to sublethal doses of both mycotoxins, by the presence in these dogs of toxic signs and lesions resembling those elicited by a single lethal dose of patulin given alone, and by the presence of pulmonary histopathology in dogs receiving both toxins at levels that, given alone, produced no such lesions. Elevated serum alkaline phosphatase in dogs given the mycotoxin combination also suggested possible interaction between the two toxins.

Interaction of secalonic acid D with phenobarbital, 3-methyl cholanthrene, and SKF-525A in mice

Secalonic acid D (SAD) is an acutely toxic and teratogenic fungal metabolite produced by Penicillium oxalium in corn and other cereal grains. Experiments were conducted to study the effects of single and multiple doses of SAD on pentobarbital-induced narcosis, as an index of the modulating effect of SAD on the hepatic drug metabolizing enzymes in mice. The effects of known enzyme modulators-phenobarbital (PB), 3-methyl cholanthrene (3-MC), and diethylaminoethyl diphenylproply acetate hydrochloride (SKF-525A)-on the acute toxicity of SAD in mice were also studied using body weights, mortality, and histopathology as indices. Results of this study failed to demonstrate any modulating effect by SAD of pentobarbital metabolizing enzymes. Pretreatment with SKF-525A, an enzyme inhibitor, enhanced SAD toxicity in mice, whereas pretreatment with PB or 3-MC, known enzyme inducers, had no effect. Further studies of interaction of [14C]SAD with PB and SKF-525A revealed that although neither PB nor SKF-525A altered the ratio of parent compound to total metabolites excreted in bile, SKF-525A significantly reduced the bile flow as well as the elimination of SAD-derived radioactivity in bile. These results strongly suggest the possibility that the effects of SKF-525A, other than the enzyme inhibition, may be responsible for its enhancement of SAD toxicity in mice.

Effects of mycotoxins on mixed-function oxidase and adenosine triphosphatase systems in neonatal rats. I. Aflatoxin B1/rubratoxin B.

Abstract The effects of aflatoxin B 1 and/or rubratoxin B on hepatic monooxygenase and hepatic, brain and renal ATPase activities were examined in neonatal rats exposed to a single treatment of one or both toxins. Animals received orally 0·4 mg aflatoxin B 1 /kg, 2 mg rubratoxin B/kg or the same doses of aflatoxin B 1 and rubratoxin B in combination, within 24 hr of birth, and were killed 12 days later. Given alone, rubratoxin B caused a statistically significant decrease in cytochrome P -450 content. Hepatic and renal oligomycin-sensitive ATPase activity was depressed by the aflatoxin B 1 and rubratoxin B combination but this effect appeared to be the result of the aflatoxin treatment. The only interaction observed after exposure of pups to the mycotoxin combination was a tendency towards a decrease in NADPH-dependent dehydrogenase.