Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

L-645, 164, a potent inhibitor of hydroxymethylglutarylcoenzyme A (HMG-CoA) reductase, is a structurally unique, synthetic monofluorinated-biphenyl that was administered to beagle dogs at dosages of 2, 10, or 50 mg/kg/day for 14 weeks to evaluate its toxic potential. Previously tested HMG-CoA reductase inhibitors from this laboratory have either been semisynthetic or fermentation-derived products containing a hexahydronaphthalene ring structure (i.e., lovastatin and simvastatin). Administration of L-645, 164 produced a significant spectrum of lesions, some of which have been previously associated with compounds of this pharmacological class, while others were unique to this monofluorinated-biphenyl inhibitor. Subcapsular lenticular opacities were produced in six of eight of the dogs receiving 50 mg/kg/day of L-645, 164 within 8 weeks of dosing. One dog receiving this dosage level experienced increases in serum alanine aminotransferase activity to levels 10 times those in concurrent control dogs. Light and electron microscopy of a wedge biopsy obtained within 3 days of this transaminase elevation failed to reveal any significant changes and the elevation resolved spontaneously despite continued drug administration. Lesions of the optic nerve and acoustic-vestibular tract and trapezoid decussation were observed in several dogs receiving 50 mg/kg/day. In addition, similar changes were observed in the optic tract in several of the dogs receiving 50 mg/kg/day and in one dog receiving 2 mg/kg/day of L-645,164. These were unique to L-645,164 and have not been observed after the administration of other HMG-CoA reductase inhibitors in this laboratory. Optic tract changes were generally mild, consisting of small to medium vacuoles without apparent myelin loss. Lesions in the other areas ranged from very slight to prominent vacuolation. No clinical signs were observed. Peak plasma drug levels of L-645,164 at 50 mg/kg were greater than 5 micrograms/ml, about one order of magnitude greater than those attained after administration of pharmacologically equipotent doses of lovastatin and simvastatin. These findings support previous observations that HMG-CoA reductase inhibitors producing high plasma drug levels are associated with a significant degree of systemic toxicity. In addition, the drug-induced CNS lesions attributed to L-645,164 appear also to be related to its chemical structure since similar lesions have not been observed after the administration of other structurally unrelated HMG-CoA reductase inhibitors that produce high plasma drug concentrations and comparable degrees of serum cholesterol lowering.
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PMID:The toxicity of a fluorinated-biphenyl HMG-CoA reductase inhibitor in beagle dogs. 205 62

Acetaminophen can be enzymatically bioactivated, which may play a role in cataractogenesis. This study evaluated the relation of dose, sex, plasma drug concentration, cytochromes P-450 (P-450 and P-448) induction, and hepatocellular toxicity to cataractogenic susceptibility in inbred mice and rabbits. C57BL/6 or DBA/2 mice, which respectively are genetically responsive and nonresponsive to P-448 induction, were treated with acetaminophen, 300 to 1000 mg/kg intraperitoneally (ip), following pretreatment with the P-448 inducer 3-methylcholanthrene (3-MC). Bilateral cataracts developed, independent of sex, in 83% of C57BL/6 mice within 4 hr of acetaminophen administration, compared with 7% of DBA/2 mice. A dose-response relation for cataractogenesis was evident in C57BL/6 mice using doses of 300 and 400 mg/kg, with the higher dose producing similar plasma acetaminophen concentrations but twofold higher glucuronide concentrations. Both strains had increased plasma concentrations of glutamic-pyruvic transaminase (GPT). New Zealand white or Chinchilla pigmented rabbits were treated with single or multiple doses of acetaminophen, 500 to 1500 mg/kg/day ip, following pretreatment with a cytochromes P-450 inducer: phenobarbital, 3-MC, or beta-naphthoflavone. Acetaminophen given chronically caused lenticular opacities within 1 week in 19 of 20 rabbits pretreated with P-450 inducers, regardless of pigmentation, but not in animals without prior P-450 induction. No opacities were observed after a single dose of acetaminophen, even with P-450 induction. There was no increase in plasma GPT in rabbits with any treatment. Over 85% of acetaminophen was recovered in urine as a glucuronide conjugate, and the rest as acetaminophen or conjugates with sulfate, cysteine, or N-acetylcysteine. Susceptibility to acetaminophen cataractogenesis can be genetically predetermined and may involve enzymatic bioactivation. possibly independent of hepatic biotransformation and toxicity.
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PMID:Pharmacological studies on the in vivo cataractogenicity of acetaminophen in mice and rabbits. 339 87