Administration of the oral antibiotic frenolicin-B selectively alters copper nutriture in male rats.

The polyketide antibiotic Frenolicin-B (FB) produces anorexia and esophageal epithelial hyperplasia (EH) in rats, findings that are characteristic of zinc deficiency. Because FB also chelates divalent cations in vitro, we conducted studies to determine whether FB modifies blood and organ concentrations of zinc and other essential metals (calcium, copper, iron and magnesium). Groups of male Sprague-Dawley rats ( approximately 250g; n = 20/group) consumed diets with adequate (40 microg/g), deficient (<2 microg/g) or fortified (100 microg/g) zinc concentrations ad libitum for 28 d. Two groups fed either Zn-adequate or Zn-fortified diets also were given 100 mg/(kg. d) of FB in diet, and 2 groups were pair-fed controls. Histopathology or metal analyses were performed on tissues from 10 rats/group. FB caused EH of the nonglandular stomach but not of other tissues. Of the metals evaluated, only copper concentrations were significantly reduced in all tissues examined except kidney. A broad range of kidney copper concentrations was found; these concentrations were associated with plasma copper and proteinaceous deposits within tubules. In rats, FB substantially and selectively depletes Cu in vivo, suggesting that drugs with structures that permit metal chelation should be evaluated for their potential to alter trace metal nutriture.

Comparative dermal pharmacology and toxicology of 4,4'-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (A-007) in rodents and primates.

4,4'-Dihydroxybenzophenone-2,4-ditrophenylhydrazone (A-007) has demonstrated anticancer activities, when administered topically to patients with metastatic cancer to the skin. Acute, subacute and subchronic dermal studies with A-007 in adult rabbits, rats, guinea pigs and monkeys failed to demonstrate local or systemic toxicity when applied topically as a 0.25% gel. A-007 did not penetrate the dermal lymphatics and did not produce detectable levels of A-007 in the plasma when applied as a 0.25% gel topically to skin. In the above studies, topically administered A-007 stimulated local sub-epithelial and dermal lymphocyte modulation, with increased CD8+ cytotoxic lymphocytes (CTL) noted, in guinea pig skin. Generally topical A-007 is well tolerated and may have useful immune modulation properties.

Toxicologic effects of an oligodeoxynucleotide phosphorothioate and its analogs following intravenous administration in rats.

The aim of the present study is to evaluate the in vivo toxicologic effects of a phosphorothioate oligodeoxynucleotide (PS oligo) and three of its analogs [PS oligo containing four methylphosphonate linkages at the 3' and 5'-ends (MBO 1), PS oligo containing four 2'-O-methylribonucleosides at both the 3'- and 5'-ends (MBO 2), and PS oligo containing an 8 bp loop region at the 3'-end (self-stabilized oligo)]. Oligodeoxynucleotides were administrated intravenously to male and female rats at doses of 3, 10, and 30 mg/kg/day for 14 days. Rats were killed on day 15, blood samples were collected for hematology and clinical chemistry determinations, and tissues, including lymph nodes, spleens, livers, and kidneys, were subjected to pathologic examinations. The toxicity profiles of the four oligodeoxynucleotides were very similar, but differed in magnitude. In terms of the severity of the abnormalities caused by the oligodeoxynucleotides, the order was MBO 2 > PS oligo > self-stabilized oligo > MBO 1. Alterations in hematology parameters included thrombocytopenia, anemia, and neutropenia. Abnormalities in clinical chemistry parameters observed with PS oligo or MBO 2 were dose-dependent elevation of liver transaminases and reduction of the levels of alkaline phosphatase, albumin, and total protein. In addition, MBO 2 caused elevation of the total bilirubin level in male rats at the 30 mg/kg dose. No major alterations in hematology or clinical chemistry were observed in rats receiving MBO 1 or self-stabilized oligo. Dose-dependent enlargements of spleen, liver, and kidney were observed, especially in rats receiving PS oligo and MBO 2. Pathologic studies showed a generalized hyperplasia of the reticuloendothelial (RE) system in the tissues examined. Alterations in the spleen were mainly RE cell hyperplasia and hematopoietic cell proliferation. In addition to RE cell hyperplasia, lymph nodes showed necrosis, hepatocytes showed cytologic alterations and necrosis, and kidneys showed renal tubule regeneration. The severity of pathologic changes observed was oligodeoxynucleotide dependent, in the order of MBO 2 > PS oligo > self-stabilized oligo > MBO 1.

Three-generation reproduction study with caprolactam in rats.

In a three-generation reproduction study, rats were given caprolactam in the diet of 0, 1000, 5000 and 10,000 ppm. No treatment-related effects were observed in the parental animals with respect to mortality, clinical signs, reproductive performance or gross pathology findings. Consistently lower body weights were noted in the P2 and P3 mid- and high-dose males and females. Consistently lower mean food consumption values were noted in the P2 and P3 mid- and high-dose males and the high-dose females. These differences were generally significant (P less than or equal to 0.05) in the high-dose group of both sexes. Compound-related histopathologic findings noted in the high-dose P1 males consisted of a slight increase in the severity of spontaneous nephropathies, occasionally accompanied by granular casts. The offspring data revealed no treatment-related effect with respect to gross appearance, gross pathology, survival, number of pups, percentage of male pups or kidney weight. Analysis of the offspring body weights on Days 1, 7 and 21 of lactation revealed consistently and generally significant lower mean values in the high-dose male and female animals of all filial generations. The mean body weights of both sexes in the mid-dose group were generally lower than those of the controls. The effects on mean body weight, mean food consumption and the group increases in the severity of nephropathy, accompanied by the presence of granular casts in some animals, are considered to be related to the administration of caprolactam.

Developmental toxicity studies of caprolactam in the rat and rabbit.

Caprolactam was evaluated for developmental toxicity potential in both rats and rabbits by the oral route. In rats dosed on days 6-15 of gestation with 100, 500 or 1000 mg/kg/day of caprolactam, the maternal survival rate was significantly lower in the high-dose group and implantation efficiencies were slightly lower in the 100 and 1000 mg/groups (but not the 500 mg/kg) than in the control. The incidence of fetal death was comparable for all groups, and the incidence of fetal viability was considerably lower in the high-dose group (but not the mid or low) than in the control group. Visceral anomalies and one visceral variant were observed in one 100 mg/kg and one 500 mg/kg pup, respectively. The anomalies included exencephaly, an incomplete left eyelid, microphthalmia (right), and a protruding tongue. No skeletal anomalies were observed. It was concluded that caprolactam at levels up to at least 500 mg/kg of body weight produced no teratogenic effects in the Fischer 344 rats. In rabbits receiving 50, 150 or 250 mg/kg caprolactam on days 6-28 of gestation, the pregnancy rate in all groups was at least 80%. The numbers of corpora lutea, live and dead fetuses, resorptions, the sex ratio and the pre- and post-implantation losses were not significantly different among the test and control groups. The incidence of major malformations and of minor skeletal anomalies was unaffected by treatment with caprolactam. Maternal weights were depressed in the group receiving 250 mg/kg. Treatment of a separate group with a positive control substance (6-aminonicotinamide) resulted in significantly (P less than 0.001) increased incidences of major malformations, minor visceral anomalies and minor skeletal anomalies. Maternal toxicity in terms of mortality was observed in pregnant rabbits treated with caprolactam at a dose of 250 mg/kg/day. Fetotoxicity was evidenced by lower fetal weights at the 150 and 250 mg/kg/day levels, and an increased incidence of thirteenth ribs was observed at the 250 mg/kg/day dose level. Neither embryotoxicity nor teratogenicity occurred at any dose level.

A two-year drinking-water study of dichloromethane in rodents. I. Rats.

In order to evaluate its toxicity and carcinogenic potential, dichloromethane (DCM) at levels of 0, 0, 5, 50, 125 and 250 mg/kg body weight/day was administered in deionized water to a total of 500 Fischer 344 rats of each sex for 104 wk. An additional group received a level of 250 mg/kg body weight/day for 78 wk followed by a 26-wk recovery period during which only deionized water was presented. Kills were performed at 26-wk intervals. Statistically significant effects on body weight, water consumption and food consumption were observed at the two highest dose levels. Minimal effects were noted on the haematological and serum chemistry parameters monitored. Treatment-related hepatic changes were observed histomorphologically in both sexes after 78 wk of treatment. These changes consisted of an increased incidence of foci/areas of cellular alteration and of fatty change at all dose levels except the lowest. A decrease in the severity of fatty change was observed in the recovery group, but no difference was noted in the incidence of cellular alteration. An increased incidence of hepatic tumours noted in females treated at 50 and 250 mg/kg/day was within the range of historical control incidences. In view of an unusually low incidence of similar tumours in the concurrent control groups and the absence of an increased incidence of hepatic tumours in the group treated at 125 mg/kg/day, the effect seen at 50 and 250 mg/kg/day was not considered to be attributable to DCM treatment. Under the experimental conditions of this study, there was a no-observable-effect level of 5 mg/kg/day in both males and females.

A two-year drinking-water study of dichloromethane in rodents. II. Mice.

To investigate its carcinogenic potential, dichloromethane (DCM) was administered at levels of 0, 0, 60, 125, 185 and 250 mg/kg body weight/day to a total of 1000 B6C3F1 mice in deionized drinking-water for 104 wk. The high-dose male and female mice showed a transitory increase in mean leucocyte counts. Treatment-related toxic changes were noted in both male and female livers at the highest dose. There was a slight elevation of proliferative hepatocellular lesions in the treated males but no dose-related trend was apparent and the effect was absent in the females. Neoplastic lesions observed in the study were homogeneous among all groups and were within the range of incidence in historical controls. The results of this study demonstrated a toxicological no-observable-effect level (NOEL) for DCM of 185 mg/kg body weight/day in both sexes.

Oncogenic evaluation of tetrachlorvinphos in the B6C3F1 mouse.

Groups of 80 male and 80 female B6C3F1 mice were fed diets containing 17.5, 64, 320, 1600, 8000, and 16000 ppm tetrachlorvinphos (TCVP) for up to 103 weeks. Another group of 80 male and 80 female mice were fed TCVP (16000 ppm) that was used in a previous bioassay. One hundred-sixty male and 160 female mice served as the control group. Ten treated and 20 control mice/sex/group were killed at 6, 12, and 18 months. It was estimated that the study maximum-tolerated dose was exceeded by three- and sixfold in the 8000- and 16000-ppm dose groups, respectively. Consequently, these exposures produced excessive cytotoxicity and regenerative changes in the liver and kidneys which were associated with sex-hormonal imbalance and metabolic overload in liver. A significant decrease (15-40%) in body weight was observed in mice fed 8000 and 16000 ppm TCVP. These treated mice did not gain weight during the study. Reduced food consumption and caloric intake throughout the study were probably responsible for the increased survival and the decreased incidence of spontaneous neoplasia in mice fed 8000 and 16000 ppm TCVP. Classification of pathologic lesions observed in these high-dose groups differed among study and consulting pathologists. The consultant and Shell pathologists concluded that the liver and kidney changes were causally related to excessive toxicity which was manifest primarily by hepatocellular hyperplasia and renal tubular adenoma. Study pathologist in accordance with his classification found statistically significant increases in hepatocellular carcinoma, hepatocellular adenoma or carcinoma, and renal tubular carcinoma in male mice fed 16000 ppm TCVP. The incidence of hepatic neoplasms as evaluated by the study pathologist in female mice fed 8000 and 16000 ppm TCVP although statistically significant was of questionable biologic significance when compared with historical female controls. The only statistically significant finding observed by the consulting pathologist was an increased incidence of renal tubular adenoma and renal tubular adenoma or carcinoma in male mice fed 16000 ppm TCVP. Use of results from these high-dose groups is contraindicated due to the many compromising factors affecting mice fed 8000 and 16000 ppm TCVP. TCVP was found not to be oncogenic in B6C3F1 mice at dose levels not exceeding the maximum tolerated dose.