Toxicokinetics of [14C]hexafluoroacetone in the rat

Detection of Effects on Male Reproduction—A Literature Survey

The 1CH (International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use) Guideline for Detection of Toxicity to Reproduction for Medicinal Products, adopted at the Second ICH Conference in Orlando, FL, U.S.A., emphasized the need for research into the suitability of various methods for the detection of effects on fertility in males. The current project was undertaken to compare the efficiency of methods by evaluating reports in the open literature. The results of the examination of 117 substances or substance classes support the view that histopathology and organ weight analysis provide the best general-purpose means of detecting substances with the potential to affect male fertility. Examinations at up to 4 weeks of treatment appear to be as effective as examinations conducted at later times. Mating with females for detection of effects unrelated to interference with sperm production appears to provide an optimal combination because adding other methodologies does not materially improve the detection rate. As to the timing of the mating trial, a 2-week premating period is as efficient as mating at 4 weeks and apparently more efficient than mating after prolonged premating treatment.

Testicular toxicity of rats exposed to hexafluoroacetone (HFA) for 90 days

Rats were exposed to 0, 0.1, 1, and 12 ppm of hexafluoroacetone (HFA) for 6 h/day, 5 days/week for 90 days. The exposed rats were killed after 30 or 90 days exposure, and 28 or 84 days post-exposure (PE). There were no exposure-related pathological lesions in the rats exposed to 0.1 or 1.0 HFA for 90 days. After 30 days exposure to 12 ppm HFA, rats showed lower body weight gain, testicular atrophy, and oligospermia or aspermia in the epididymal tubules. At 30 days exposure, the atrophic testes had marked depletion of round spermatids in spermatogenic stages I-VIII and elongated spermatids in spermatogenic stages IX-XIV, but mature spermatids appeared only slightly decreased. Numerous spermatocytes in meiotic division in spermatogenic stage XIV were necrotic. At 90 days exposure, the testes showed severe atrophy with almost all seminiferous tubules affected and both immature and mature spermatids had disappeared from the seminiferous tubules. The epididymal tubules were devoid of spermatozoa. After 28 days PE, regeneration of atrophic testes was evident but varied markedly among the exposed rats. The number of seminiferous tubules producing elongated and mature spermatids was significantly lower than that of normal testes. Many seminiferous tubules had not regained normal spermatogenesis and the epididymal tubules showed marked oligospermia. After 84 days PE, normal spermatogenesis was still only partially restored to the atrophic testes, with many of the regenerating tubules still devoid of normal spermatogenesis.

Toxicology of fluorine-containing monomers

Fluorine-containing monomers form the basis for production of a large number of commercially important polymers. Most of the polymerization occurs as gas-phase reactions, hence the hazards associated with the monomers arises primarily from inhalation. The chemicals covered in this review include bromotrifluoroethylene (BTFE), chlorotrifluoroethylene (CTFE), hexafluoroacetone (HFA), hexafluoroisobutylene (HFIB), hexafluoropropylene (HFP), perfluorobutylene (PFBE), tetrafluoroethylene (TFE), trichloropropene (TFP), vinyl fluoride (VF), and vinylidene fluoride (VF2). The amount of toxicologic information available on the compounds is relatively small and for certain of these the information consists is short-term or acute, hence the current need to make predictions of biologic activity based on analogy or chemical reactivity is great. In animal models and in man, these monomers may be absorbed into the body at varying rates and the metabolism ranges from extensive to little in a species, dose, and chemical specific fashion. The major toxicologic target of these materials is the kidney, and the degree of involvement depends greatly on the excretion patterns and metabolic profiles of the monomers. However, other target sites exist, such as the reproductive system for HFA, making the use of structure-activity relationships difficult.

Effects of hexafluoroacetone on Leydig cell steroidogenesis and spermatogenesis in the rat

Steroidogenesis was investigated in Leydig cell-enriched fractions isolated from the testes of rats dosed dermally with 130 mg/kg/day hexafluoroacetone (HFA) for 14 days and from pair-fed control rats. Compared to controls, Leydig cells from HFA-treated rats exhibited decreased incorporation of [14C]acetate (78%) and [3H]mevalonate (41%) into sterols and steroids. Testosterone was decreased 50% in the testes of HFA-treated rats. Incubation of Leydig cells from untreated rats with 1.0 mM HFA did not affect steroidogenesis. HFA treatment led to the development of histopathological lesions in the testes within 24 hr after a single dose; with daily dosing the lesions became progressively more severe. Despite the development of severe lesions, HFA treatment did not affect the blood levels of luteinizing hormone or testosterone; however, follicle-stimulating hormone was slightly elevated (48%) after 14 days of treatment. The data indicate that steroidogenesis is inhibited in Leydig cells of HFA-treated rats; the inhibition is not due to a direct or immediate effect of HFA, nor does it appear to be hormonally mediated.