Denise A. Leonard

Evaluation of a rodent peroxisome proliferator in two species of freshwater fish : rainbow trout (Onchorynchus mykiss) and Japanese medaka (Oryzias latipes)

Rainbow trout (Onchorynchus mykiss) and Japanese medaka (Oryzias latipes) were exposed to the hypolipidemic drug gemfibrozil, a known rodent peroxisome proliferator. Trout were injected (i.p.) daily for 2 weeks at doses of 0, 46, 87, or 152 mg/kg/day. Medaka were exposed to the nominal concentrations of 0, 1.25, 2.5, or 5 ppm in water for 2 weeks in a static-renewal system. Peroxisome proliferation was assessed by measuring fatty acyl-CoA oxidase (FAO) activity, peroxisomal bifunctional enzyme (PBE) quantity, and changes in liver-to-body weight ratios (LWR). Results indicate that a mild peroxisome proliferative response was observed in rainbow trout (significant increases in FAO activity at all dose levels and in LWR at the highest dose level). Medaka demonstrated a significant increase in PBE at the highest dose level, while nonsignificant increases in FAO activity were observed at the mid- and high-dose levels.

The Effects of Vitamin C Supplementation on Blood and Hair Levels of Cadmium, Lead, and Mercury

Fifty‐two adult male subjects were randomly assigned to one of three possible treatment groups: supplemental ascorbic acid at one of two levels, 500 mg or 1000 mg, or a placebo. Hair and blood samples were taken before vitamin C or placebo supplementation was started and at monthly intervals thereafter for three months. Samples were analyzed for cadmium, lead, and mercury. Results indicate that vitamin C did not significantly affect levels of these metals in either hair or blood samples.

Effects of chlorite exposure on conception rate and litters of A/J strain mice

The use of chlorine has been almost universally accepted as the method of choice for disinfecting potable water supplies. However, recent studies have demonstrated that the interaction of chlorine with ubiquitous and naturally occurring humic acids in water results in the formation of trihalomethanes (U.S. EPA 1975, ROOK 1976) some of which are known or suspected carcinogens (MARX 1974, U.S. EPA 1975, DEROVEN & DIEM 1975a, U.S. EPA 1977a). Among these, chloroform has been shown to produce hepatomas in selected mouse and rat strains in the exposure range of 90 to 447 mg/kg of body weight (ANONYMOUS 1976, ROE 1976).

Role of Tissue Repair in Carbon Tetrachloride Hepatotoxicity in Male and Female Sprague-Dawley and Wistar Rats

This study was designed to assess the hypothesis that large differences between male and female Wistar and Sprague-Dawley rats in susceptibility to carbon tetrachloride (CCl4)-induced hepatotoxicity are related to the differential capacity to repair tissue damage. This hypothesis was evaluated via two complementary approaches, (a) Separate groups of rats were administered a minimum lethal dose (LD10) of CC14, with colchicine (CLC) given at 24, 48, or 72 h after CCl4, and assessed for survival, (b) Rats were given a modestly hepatotoxic dose of CC14 and evaluated in terms of the rate and magnitude of damage and the efficiency of repair activities. The mortality for Wistar rats was high for both males (70%) and females (90%) treated with CLC at 24 h after CC14 administration but fell to 33% for females while remaining high (67%) for males treated with CLC at 48 h after CC14 administration. Both male and female Sprague-Dawley rats also exhibited a high mortality rate (70–80%) when administered CLC 24 h after CC14. As in the Wistar rats, the mortality in the Sprague-Dawley females declined to 36% while it remained high among males (67%) when CLC was administered 48 h after the CC14 dose. Male and female Wistar and Sprague-Dawley rats were dosed with CC14 (0.3 ml/kg, 1:1, vol/vol in corn oil, i.p.), and the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were monitored at 0, 24, 48, and 72 h after treatment. In the Sprague-Dawley strain, AST and ALT values were markedly increased in the female as compared with the male at 24, 48, and 72 h. Both sexes displayed decreasing serum enzyme values starting at 48 h. In contrast to Sprague-Dawley rats, male Wistar rats showed progressive increases and significantly higher AST/ALT values than the females at 48 h; conversely, by 48 h the female rats were starting to display decreasing serum enzyme levels indicative of tissue repair. The findings support the hypothesis that the enhanced susceptibility to CCl4-induced hepatotoxicity of the male compared with the female Wistar rat is principally due to a slower capacity for hepatic tissue repair. In contrast, the principal cause for the enhanced susceptibility of the female compared with the male Sprague-Dawley rat to CC14-induced hepatotoxicity is most likely related to its greater susceptibility for the production of liver damage rather than a less efficient tissue-repair process. Key Words: Carbon tetrachloride-Hepatotoxicity-Sex differences-Tissue repair

Effects of Joint Exposures to Selected Peroxisome Proliferators on Hepatic Acyl-CoA Oxidase Activity in Male B6C3F1 Mice

The interaction potential of peroxisome proliferators of similar and dissimilar structure was examined in B6C3F1 mice. Mice were fed diets containing varying concentrations of ciprofibrate (Cipro), clofibrate (Clof) or di(2-ethylhexyl)phthalate (DEHP), or combinations of Cipro and Clof or Cipro and DEHP for 4 d. Induction of peroxisomal beta-oxidation, measured by increased acyl-CoA oxidase activity, was used as the endpoint for analysis. An additive response occurred following joint exposure to the structurally related compounds Cipro and Clof, whereas a possible synergistic response occurred at low dose combinations of the structurally dissimilar Cipro and DEHP. These findings represent the first report assessing the in-vivo interaction potential of structurally similar and dissimilar peroxisome proliferators and provides insight into the dose-response nature of joint exposures to certain non-genotoxic carcinogens.

interactive Potential of Omega-3 Fatty Acids with Clofibrate or DEHP on Hepatic Peroxisome Prolifieration in Male Wistar Rats

The interactive potential of three known peroxisome proliferators, omega-3 fatty acids, clofibrate and di(2-ethylhexylphthalate (DEHP), was evaluated in male weanling Wistar rats for the effect on peroxisomal beta-oxidation. Omega-3 fatty acids were supplied by menhaden oil which was fed in six regimens: low fat (5% w/w), low fat and clofibrate (0.3% w/w) or DEHP (0.25% w/w), high fat (20% w/w), high fat and clofibrate or DEHP in the aforementioned concentrations. Induction of peroxisomal beta-oxidation was measured by changes in liver-to-body weight ratio, fatty acyl-CoA oxidase (FAO) activity, and peroxisomal bifunctional enzyme (PBE) quantity. Analysis of transformed data indicated a less than additive response in FAO activity with no deviation from additivity seen with liver-to-body ratios and PBE.

The in vivo effects of four steroids on glucose‐6‐phosphate dehydrogenase activity of c57L/J mouse erythrocytes

Abstract Preliminary dose‐response relationships were established by in vitro incubation of dehydroepiandrosterone (DHEA) and epiandrosterone (EPI) with human blood. DHEA in increasing concentration resulted in 61% to 76% inhibition of erythrocyte G‐6‐PD activity, while EPI in increasing concentration resulted in 69 to 85% inhibition (p = .001). In vivo tests were conducted using G‐6‐PD‐low C57L/J mouse erythrocytes. Mice were orally administered 0.2 ml of 450 or 900 mg/kg of DHEA, EPI, pregnenolone (PREG) or androstanedione (ANDR) every other day for seven days (four doses) and sacrificed three hours after the final dose. Blood samples revealed no significant reductions in G‐6‐PD activity, possibly due to a lack of receptor sites for the steroids on the erythrocyte membrane.

The effects of dehydroepiandrosterone and ethanol on acetylphenylhydrazine‐stressed human erythrocytes

Abstract The hormone, dehydroepiandrosterone (DHEA), has been shown to inhibit red blood cell and tissue G‐6‐PD activity levels, in vitro. Red blood cell samples fron six adult human subjects were collected in order to evaluate DHEA‐treated erythyrocyte responses to the oxidant stressor agent, acetylphenylhydrazine (APH). Human erythrocytes were incubated with DHEA for half an hour, then with with 0.5 to 5.0 mg APH for one to two hours. Methemoglobin and reduced glutathione levels were measured after incubation. The erythrocytes treated with DHEA were sensitive to the oxidant Stressor effects of all levels of APH, compared to the responses of normal red blood cells. However, erythrocytes treated with the ethyl alcohol carrier were similarly sensitive to the oxidizing effects of APH.

Effects of Repeat Dosing and Multiple Blood Drawing Separately and Together on Carbon Tetrachloride–Induced Hepatotoxicity

A series of experiments was conducted to assess the effects of prior dosing and/or multiple modest blood withdrawal on subsequent carbon tetrachloride (CCl4)-induced hepatotoxicity. Adult male Wistar rats were randomly assigned to the following treatments: oil-CCl4, oil-bleed-CCl4, CCl4-CCl4, and CCl4-bleed-CCl4, with bleed groups having 1 ml of blood removed at baseline (time 0), 24, 48, 72, and 120 h. At these times the levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were determined. The serum enzyme levels of the CCl4 (0.9 ml/kg, vol/vol in corn oil, per os) treated rats (treated at time 0) had returned to untreated levels prior to the administration of the second dose (120 h). Serum enzyme (AST/ALT) levels were measured again 24 and 48 h after the second CCl4 (0.9 ml/kg, 1:1 vol/vol in corn oil, per os) treatment. The results indicated that the prior dose of CCl4 (0.9 ml/kg, 1:1 vol/vol in corn oil, per os) enhanced the hepatotoxicity of a subsequent identical dose of CCl4 three- to six-fold when the two doses were separated by 2–14 days, although the prior dose was protective when administered 24 h before the second dose. Prior multiple blood drawing also enhanced the hepatotoxicity of a subsequent dose of CCl4 (0.9 ml/kg, 1:1 vol/vol in corn oil, per os) three-fold. The effect of blood drawing has been demonstrated to cross sex and strain when tested on male and female Sprague-Dawley and Wistar rats. The combination of the two procedures (with the two CCl4 doses separated by 5 days) enhanced the hepatotoxicity of a subsequent identical dose of CCl4 (0.9 ml/kg, 1:1 vol/vol in corn oil, per os) 10-fold. Subsequent sham bleed experiments indicated that the increase in serum enzyme levels previously associated with blood withdrawal is substantially associated with the handling (i.e. stress) involved in blood withdrawal rather than the removal of modest amounts of blood per se.

The effect of 3‐methylcholanthrene‐induced increases in ascorbic acid levels on tissue β‐glucuronidase activity in rats

The interrelationship between tissue ascorbic acid levels and tissue ..beta..-glucuronidase activity was examined in rats injected with 3-methylcholanthrene, an agent which induces ascorbic acid synthesis in rats. Six Fisher 344 rats were dosed intraperitoneally (IP) with 30 mg/kg of 3-methylcholanthrene. Ascorbic acid levels and ..beta..-glucuronidase (..beta..-G) activity were determined for lung, liver and kidney tissues. In a follow-up study, rats were dosed for three consecutive days with 3-methylcholanthrene. Controls in both groups were dosed IP with Emulphor (EL-620). Animals were sacrificed one week after the final dosage and lung, liver and kidney tissues were examined.