H. Jackson

Studies with alkylating esters. II. A chemical interpretation through metabolic studies of the antifertility effects of ethylene dimethanesulphonate and ethylene dibromide.

Abstract The metabolism of 1,2- 14 C-ethylene dimethanesulphonate (EDS) has been followed in the rat and mouse and compared with that of 1,2- 14 C-ethylene dibromide (EDB). EDS is excreted unchanged in urine together with S-(2-hydroxyethyl)-cysteine N -acetate and S-(2-hydroxyethyl)-cysteine- N -acetate-S-oxide. EDB is not excreted unchanged but is metabolised mainly to S-(2-hydroxyethyl)-cysteine and its N -acetate. The distribution of radioactive label in mouse tissues is different for both compounds which may indicate a difference in the origin of cysteinal units for alkylation. Both ethylene dimethanesulphonate and ethylene dibromide react efficiently in vitro with SH containing compounds by a reaction analogous to the “sulphur stripping” action of Myleran, although the metabolism of EDS and EDB would not indicate such a reaction takes place in vivo. The antispermatogenic actions of EDS differ from those of its homologues, such as Myleran, but show some resemblance to those of EDB. These effects of EDS and EDB may indicate that both compounds have latent “mustard-like” activity, and this possibility is discussed in terms of the pharmacological effects produced by EDS and its chemical reactions with nucleophiles.

Antifertility Effects and Metabolism of α and epi-Chlorhydrins in the Rat

THE ability of a variety of alkylating chemicals to produce infertility in male animals has long been established1 and investigations have shown that many such compounds are capable of alkylating genetic materials2. Their mutagenic effects in insects3 and the induction of dominant lethal mutations in experimental rodents4,5 are presumably the result of such interactions.

Studies with alkylating esters—I: The fate of ethylene dimethanesulphonate

Abstract The fate of 14 C- and 35 S-ethylene dimethanesulphonate (EDS) has been studied in the mouse, rat, rabbit and monkey and compared with that of Myleran, a homologue of EDS. The rat and mouse excreted mainly unchanged 35 S-EDS, whereas from the rabbit and monkey only a minor proportion of the unhydrolysed ester was recovered in the urine. Methane sulphonic acid was the only radioactive urinary metabolite, and in this respect no species variation was encountered. In the rat 1,2- 14 C-EDS gave no evidence of simple hydrolysis since ethylene glycol was not found as a urinary metabolite. Expired radioactive carbon dioxide accounted for 5–8 per cent of the dose. Tissue distribution studies in the mouse show bone, blood and spleen have some selective uptake of EDS; the compound is only slowly cleared from these tissues. The relevance of the findings are discussed and related to comparable studies with Myleran in relation to the biological activity of both compounds.

Metabolic studies of 32P-labelled triethylenethiophosphoramide

Abstract Triethylenethiophosphoramide (ThioTEPA) labelled with radioactive phosphorus has been prepared and its metabolism examined in the rat, mouse, dog and rabbit. The drug was metabolized rapidly in vivo . The primary stage was the rapid replacement of S by O with the formation of TEPA. The mouse was exceptional in that the compound was degraded so that the principal radioactive metabolite excreted was inorganic phosphate In the rat, TEPA was the main metabolite; but the dog and rabbit excreted three other metabolites, although the major product was TEPA. There was no specific localization of labelled material in the tissues of the mouse and rat apart from the retention of some radioactivity in the protein part of rat haemoglobin. The results suggest that this type of alkylating agent, in spite of its biological activity is not highly reactive chemically in vivo .

Characterization and antifertility activity in rats of S(+) α-chlorohydrin

The S(+)-isomer of alpha-chlorohydrin is characterized and its antifertility activity in rats was investigated. The R(-)-isomer has shown neither reversible antifertility effects nor permanent sterilizing capability and is more toxicthan the racemic mixture. A single oral dose of the S(+)-isomer (12.5 mg/kg) produced temporary infertility in 5 male rats. Their reproductive function returned to normal during the 2nd week after treatment. A higher dose induced sterility during the 1st week some recovery during the 2nd and 3rd weeks followed by a permanent sterilizing effect. It appears that the initial period of infertility is caused by an action on epididymal sperm while the permanent effect is due to bilateral and irreversible blockage of the vasa efferentia following damage to the epithelium of the caput epididymis. It seems that the S(+)-isomer of alpha-chlorohydrin is about twice as active as the racemic compound. Preliminary toxicity studies showed that the S(+)-isomer was not lethal at 150 mg/kg.

Spermatogenic and Mutagenic Damage after Paternal Exposure to Systemic Indium-114m

The cytotoxic and mutagenic consequences of systemic administration of 114mIn have been examined. Adult male rats were dosed intraperitoneally with 14.8 or 3.7 MBq/kg 114mIn. Approximately 0.25% of the injected radioactivity was localized within the testis by 24 h and was retained with an effective half-life of 49.5 days. Breeding studies were started 3 days after injection, males being housed with two females for seven consecutive mating trials of 19 days, separated by 2 days. Indium-114m caused a reduction in litter size and an increase in the incidence of pre- and postimplantation losses and dominant lethal mutations. These effects became evident from 24 days but were most marked between 87-126 days after treatment and persisted up to 147 days. When animals were mated 200 days after treatment, no significant changes were observed. In a parallel study, administration of 14.8 MBq/kg 114mIn resulted in decreased testis and epididymal weight and sperm reserves. Maximal reduction occurred between 87-108 days after injection followed by recovery toward control values, but neither organ had reached normal levels at 200 days. A single dose of 3.7 MBq/kg, however, had no effect on reproductive organ weight or sperm content. Male F1 progeny from the 14.8 MBq/kg group of the second mating period (commencing at 24 days) displayed decreased testis weights and sperm content and provoked a higher incidence of dominant lethal mutations. This effect was not observed in male progeny from any other time or the alternative dose level.

The antifertility effects of α-chlorohydrins and their stereo-isomers in male rats

The antifertility effects of alpha-chlorohydrins and their stereo-isomers were investigated in male rats. A single oral dose of 50 mg dl-alpha-chlorohydrin induced sterility in the 1st week with normal f ertility in the 2nd followed by a decline to sterility by Week 4 which was permanent. This was due to bilateral obstructive lesions (sperm granulomata) in the ductuli efferentes. A similar dose of R-1-isomer representing the amount contained in 100 mg/kg dose of dl-alpha-chlorohy drin resulted in normally fertile rats over the 6-week study period. High doses of either dl or 1-1-amino-3-chloro-2-propanol were incompletely effective in producing sterility. A single oral dose of 100 mg R-1-alpha-chlorohydrin was lethal to 6 of 6 rats whereas only 5 of 12 succumbed to a similar dose of the dl-mixture. Further studies of the effects of dl-alpha-chlorohydrin (50 mg/kg 5 days/week) on the hemopoietic tissue are in progress.

The comparative metabolism of myleran-35S in the rat, mouse and rabbit

Abstract The fate of Myleran- 35 S has been examined in three species. The rat and mouse excretes 35 S-labelled materials in similar proportions, whereas the rabbit excretes only methane sulphonic acid- 35 S. The rabbit appears to be deficient in the urinary component which combines with methane sulphonic acid in the rat and mouse.

A comparative binding of platinum anti-tumour compounds to plasma proteins in the rat (in vivo) and mouse (in vitro)

Plasma protein binding of 195mPt-labelled cisplatin, carboplatin and iproplatin has been studied in vivo in rat and in vitro in mouse, using both electrophoresis and trichloroacetic acid precipitation. After intravenous injection plasma clearance rates were biphasic for all 3 compounds, (t1/2 alpha, 13-17 min) but cisplatin was retained thereafter longer than the others. By 5 min, gel electrophoresis showed protein labelling with all 3 drugs but none involved low mol.wt. proteins (< 16 kDa). At 2 h a notable proportion of the protein bound platinum was associated with the latter components. There was a general resemblance between the distribution patterns of cisplatin and carboplatin whereas iproplatin showed a persistent retention of the label with time to higher mol. wt. proteins. From in vitro incubation with mouse plasma, rates of interaction respectively were cisplatin t1/2 alpha, 35 min, beta 8 h, carboplatin t1/2, 44 h and iproplatin t1/2, 104 h. By electrophoresis the protein bound fraction pattern (1 h) was again similar for cisplatin and carboplatin with virtually no binding to low mol. wt. proteins. After 24 h these were now involved to a high degree (40%). Iproplatin showed relatively marked binding to proteins of higher mol. wt. but no transfer with time to the low mol. wt. protein zone. A possible explanation is the need for in vivo metabolism for this compound as manifest in the rat. It is suggested that the significance of interaction with low mol. wt. proteins merits further investigation in relation to the antitumour and toxicological actions of these drugs.

Metal radionuclides and the testis

SummaryRadioactive 114mIn from plasma proteins localises and is retained in developing rat spermatozoa.