Studies with alkylating esters. VI. The chemical and biological activities of the isomers of dimethylmyleran

Toxicological review of busulfan (Myleran)

Busulfan is a bifunctional alkylating agent that appears to be cytotoxic to slowly proliferating or non-proliferating stem cell compartments, although its specific molecular and cellular mechanisms are unknown. It is the drug of preference in treatment of chronic myelogenous or granulocytic leukemia because its cytotoxic activity results in primary damage or destruction of hematopoietic cells. Additional effects resulting from the cytotoxicity of busulfan in hematological and other tissues, as documented by both human and animal model studies, include lethality, sterility, teratogenicity, and alteration of immune function. Busulfan has been shown to be mutagenic to microorganisms, mammalian cells in culture, Drosophila, and rodents. This agent is also considered potentially carcinogenic to humans. Various tissue hyperplasia and preneoplastic cells have been observed in animal model studies with busulfan, and case reports on human patients implicate busulfan as the causative agent in induction of secondary malignancies. Reports from human and animal studies of busulfan's cytotoxicity, teratogenicity, carcinogenicity, and mutagenicity have been reviewed. This information may be useful in a quantitative assessment of the effects of this agent and the identification of significant deficiencies in the data base. Demonstration that busulfan induces mutations in both somatic and germ cells suggests the need to assess its risk to humans.

Comparative effect of the isomers of dimethylmyleran on spermatogenesis in the rat

Both meso- and racemic forms of dimethylmyleran are powerful antispermatogenic agents which cause a rapid depletion in the number of type A spermatogonia. A block on their proliferation causes a progressive depopulation of maturing germ cells in the seminiferous epithelium. Each isomer produces maximal reduction of Type A by 2 weeks and their recovery thereafter leads to restoration of the germ cells. Histological analysis of cell changes in the testis infers that Type A at Stage VII of the cycle of the seminiferous epithelium is susceptible to the action of the meso and +/- isomer, but the mixture interferes with Type A at Stages VII-XIV. Stem cell Type A survive treatment seemingly in normal number. During repopulation, the yield of Intermediate Type spermatogonia from Type A was relatively low for several weeks, after the use of the meso isomer, indicating the persistence of damage to the latter. An insufficient recovery period did not permit complete spermatid restoration.

The metabolism of 3-chloro,- 3-bromo- and 3-iodoprpan-1,2-diol in rats and mice

1. The metabolism of the 3-halopropan-1,2-diols (alpha-halohydrins) has been investigated in rats and mice. Apart from 3-chloropropan-1,2-diol (I), of which some 10% is excreted unchanged by both species, the compounds are completely degraded following intraperitoneal administration. 2. The alpha-halohydrins are detoxicated by conjugation with glutathione and produce two urinary metabolites, isolated and identified as S-(2,3-dihydroxypropyl)cysteine (VII) and the corresponding mercapturic acid N-acetyl-S-(2,3-dihydroxypropyl)cysteine (VIII). 3. When incubated with rat liver supernatant, the compounds do not conjugate with glutathione and their general chemical reactivity suggests that they react via a common intermediate proposed to be glycidol (2,3-epoxypropanol, IV). As the epoxide produces the same urinary metabolites as the alpha-halo-hydrins, and conjugates with glutathione either with or without liver supernatant to form the primary metabolite S-(2,3-dihydroxypropyl)glutathione (VI), glycidol is also proposed to be the reactive intermediate in vivo. 4. The role of epoxides in intermediary metabolism is discussed.