Acute toxicity study of 1,3,3,5,5-pentaziridino-1-thia-2,4,6-triaza-3,5-diphosp horine-1-oxide (a new antitumor agent with an inorganic ring) in mice, rats and dogs

In order to study the safety of 1,3,3,5,5-pentaziridino-1-thia-2,4,6-triaza-3,5-diphospho rine-1-oxide (SOAz), a new antitumor agent, acute toxicity studies by intravenous administration were performed in ddY mice, Wistar rats and beagle dogs. The LD50 values in rodents were 325 mg kg-1 for male mice, 450 mg kg-1 for female mice, 100 mg kg-1 for male rats and 82 mg kg-1 for female rats. In dogs, the LD50 values were 12 mg kg-1 for males and 18 mg/kg-1 for females. The dosed animals showed diarrhoea and decreased movement in the three species, and emaciation and loss of body weight in mice and rats. Dogs also showed signs of pneumonia. Histopathological examination revealed bone marrow suppression, atrophy of lymphoid organs and testes, and damage to the digestive tract mucosa in the three species. The main causes of death from single-dose administration were bone marrow aplasia and atrophy of lymphoid tissue in all species, together with gastro-intestinal ulceration in rats and dogs, and infection in mice and dogs.

Decreased cytotoxicity of aziridinylbenzoquinone caused by polyamine depletion in 9L rat brain tumor cells in vitro

The in vitro cytotoxicity of aziridinylbenzoquinone (AZQ) used either alone or after induced intracellular polyamine depletion in 9L rat brain tumor cells was studied using a colony-forming efficiency assay. Used alone, AZQ was cytotoxic to 9L cells; however, depletion of intracellular putrescine and spermidine levels by treatment with 1 mM alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, for 72 hr decreased significantly the cytotoxicity of AZQ. Dose modification factors were 1.9 and 1.8 at 10 and 1% survival levels, respectively. Decreased cytotoxicity could be almost completely prevented by addition of putrescine to polyamine-depleted cells 24 hr before AZQ treatment. Although AZQ alone was cytotoxic against 9L cells, metabolic activation by the S-9 rat liver microsomal fraction increased greatly the observed cytotoxicity. However, even with microsomal activation, pretreatment of cells with 1 mM alpha-difluoromethylornithine for 48 hr produced a significant decrease in AZQ cytotoxicity; dose modification factors were 2.4 and 2.2 at 10 and 1% survival levels, respectively. Addition of putrescine to polyamine-depleted cells 24 hr before AZQ treatment prevented the decrease in cytotoxicity. Pretreatment of 9L cells for 48 hr with 40 microM methylglyoxal bis(guanylhydrazone), a polyamine biosynthesis inhibitor that competitively inhibits S-adenosylmethionine decarboxylase, caused a decrease in the cytotoxicity of AZQ administered without microsomal activation. The dose modification factor was 1.6 at both 10 and 1% survival levels.

Phase II and pharmacokinetic study of aziridinylbenzoquinone [2,5-diaziridinyl-3,6-bis(carboethoxyamino)-1,4-benzoquinone, diaziquone, NSC 182986] in high-grade gliomas

2,5-Diaziridinyl-3,6-bis(carboethoxyamino)-1,4-benzoquinone (AZQ; Diaziquone, NSC 182986) is a rationally designed antitumor drug possessing sufficient lipid solubility to allow penetration into the central nervous system. Thirty-one patients with high-grade glioma and progressive disease following radiation, with or without previous chemotherapy, have been treated with 144 cycles of drug, consisting of 20 mg/sq m given as an i.v. infusion on Days 1 and 8 of a 28-day cycle. Responses were measured by serial computer tomography scanning. Of the 28 evaluable patients, 6 (21%) had limited improvement (10 to 40% reduction in tumor size) on computer tomography scan, 10 (36%) had disease stabilization, and 12 (43%) had progressive disease. The drug was well tolerated clinically, with little acute toxicity. The major toxicity was myelosuppression, which appeared cumulative, using this dose regimen. AZQ was measurable in both tumor tissue and tumor cyst fluid in patients on therapy. Plasma samples taken during the period of infusion confirm that 50% or more of the total AZQ exposure occurs during the infusion period. AZQ behaves as intended by design and demonstrates activity in this poor-prognosis group of patients.

Selective presynaptic cholinergic neurotoxicity following intrahippocampal AF64A injection in rats

Compound AF64A, ethylcholine mustard aziridinium ion (0.4-8 nmol) was stereotaxically administered into rat dorsal hippocampus, and neurochemical changes were determined 5 days later. AF64A treatment, over an almost 10-fold dose range, resulted in a significant (up to 70%) decline in choline acetyltransferase activity. In the same tissue samples, Na+-dependent choline transport activity was also lowered, with most decreases ranging between 10 and 50% of controls; however, there was no significant correlation (r = 0.39) between these two parameters. Acetylcholinesterase activity was not affected by AF64A treatment when assayed by either histochemical or enzymatic methods. AF64A reduced acetylcholine levels by 43%, but did not alter norepinephrine content or serotonin uptake. These results demonstrate that AF64A can induce a specific, long-term reduction of cholinergic presynaptic biochemical markers in rat hippocampus. Thus, AF64A can serve as a useful new tool to study the cholinergic system and as an important agent to help develop animal models representing disorders of central cholinergic hypofunction.

Selective inhibition of peripheral cholinergic transmission in the cat produced by AF64A

The neuropharmacologic effects of ethylcholine aziridinium ion, AF64A, were studied in cats, using various physiological techniques, to ascertain its synaptic site of action and to determine whether it may act as a cholinergic specific neurotoxin in vivo. Nictitating membrane contractions elicited by preganglionic nerve stimulation (1-16 Hz) were diminished in a dose-dependent manner after injection of AF64A into the carotid artery. Contractions due to injection of l-norepinephrine, tetramethylammonium or acetylcholine were not changed. Postganglionic action potentials from the superior cervical ganglion evoked by preganglionic stimulation were also abolished by AF64A, whereas the postganglionic firing produced by tetramethylammonium was unchanged. Neither the nictitating membrane nor ganglionic responses on the contralateral side of the animal were affected by AF64A treatment. In the same animals, twitch tension in the tongue produced by stimulation of the ipsilateral hypoglossal nerve (1-16 Hz) was gradually reduced and in most experiments completely blocked by AF64A. Repetitive stimulation of either the autonomic or somatic nerves at high frequencies (greater than 10 Hz) magnified and accelerated the onset of neurotoxic effects of AF64A. The suppression of ganglionic and neuromuscular transmission by AF64A was irreversible during the course of the experiments (12-18 hr). From these results, we can conclude that AF64A produces in the peripheral nervous system a longlasting inhibition of cholinergic transmission, without interfering with adrenergic transmission. Moreover, because AF64A did not block the postganglionic responses elicited by cholinergic nicotinic and muscarinic agonists, the inhibitory effects of AF64A must be mediated by a presynaptic action on cholinergic nerve terminals.

Effect of 1,3,3,5,5-pentaziridino-1-thia-2,4,6-triaza-3,5-diphosphorine-1-oxide, a new antitumor agent with inorganic ring, on various experimental tumors

1,3,3,5,5-Pentaziridino-1-thia-2,4,6-triaza-3,5-diphosphorine-1-oxide (SOAz), a new antitumor agent, was evaluated for antitumor activity against various mouse- and rat-tumor systems. The optimal treatment regimens of SOAz (i.p.) gave 262% and 134% increase in life span (ILS) in mice with P388 leukemia and L1210 leukemia implanted intraperitoneally, respectively, and 239% ILS in rats with Yoshida sarcoma of which 86% survived for 60 d after intraperitoneal tumor implantation. The compound showed a definite activity against Lewis lung carcinoma implanted intravenously. The compound also exhibited 80-100% inhibition of tumor local growth in all of four experimental tumor systems used in the present study. In contrast to cyclophosphamide, SOAz was active against B16 melanoma and Meth A, and demonstrated high activity against a subline of L1210 leukemia resistant to cyclophosphamide.

Factors influencing the severity and progress of ethylenimine-induced papillary necrosis

The severity of the renal papillary necrosis produced in rats by ethylenimine is dependent both on dose and urinary concentration within the medulla. When this is reduced by diuresis, the severity of the lesion is effectively reduced. Increasing urinary concentration has a reverse effect, but of less magnitude. When the concentrating power of the renal medulla is impaired by a single dose of ethylenimine, insufficient to cause necrosis of the whole papilla, further doses of ethylenimine do not cause progressive damage to the papilla.

Testicular damage and change in serum LDH isozyme pattern induced by multiple sub-lethal doses of apholate in albino rats

Treatment with apholate caused degenerative changes in the testes of albino rats. No histological changes were observed in Leydig cells. LDH-X activity was present in the serum of treated rats and absent in controls. Electrophoresis indicates that the activity band present in serum was similar to the activity band found in testes. A colorimetric method for assaying LDH-X activity is reported.

Interaction of endosulfan and metepa in rats

Repeated administration of endosulfan or metepa or their mixture did not induce any significant histological changes in the organs examined in male rats. Similarly, the activity of different enzymes assayed here showed no significant alterations. The level of endosulfan did not differ significantly in presence or absence of metepa in the samples of blood, brain, fatty tissue, kidney, liver and testis. The observations do not suggest any kind of additive or antagonistic effects or potentiation of each compound in presence of the other, at the doses and duration studied in male rats.