Effect of ascorbic acid on the consequences of acute alcohol consumption in humans.

This study examines the influence of ascorbic acid pretreatment on ethanol clearance, toxicity, and behavioral impairment after an acute dose of ethanol in humans. Ascorbic acid or a placebo was given to 20 healthy male subjects for 2 weeks before ethanol consumption. The dose of ethanol was 0.95 gm/kg body weight and was consumed during a 2 1/2-hour period. Thirty minutes after ethanol consumption, motor coordination and intellectual function were assessed by Goldberg's "Finger-Finger" and "Serial Sevens" tests. In addition, color discrimination was measured with the use of the Farnsworth-Munsell 100 Hue Color Test. Hourly blood samples were taken for 10 hours after ethanol consumption to measure serum triglyceride levels, blood lactate/pyruvate ratios, and serum enzymes. Blood ethanol clearance was also determined. Ethanol consumption elevated serum triglyceride levels and blood lactate/pyruvate ratios and impaired performance of the behavioral tests but did not alter serum enzyme levels. Ascorbic acid pretreatment resulted in significant enhancement in blood ethanol clearance and an increase in serum triglyceride levels after ethanol consumption in half of the subjects. Ascorbic acid pretreatment also resulted in improved motor coordination and color discrimination after ethanol consumption in half of the subjects. Ascorbic acid pretreatment did not influence elevated blood lactate/pyruvate ratios or impaired intellectual function.

Ascorbic acid and alcohol oxidation.

Methanol and ethanol were rapidly metabolized to formaldehyde and acetaldehyde in the presence of ascorbate, 1,10-phenanthroline and either guinea pig hepatic 100,000 g supernatant or 12,000 g pellet fractions. The specific activity of methanol oxidation was 1720 nmoles formaldehyde formed/min/mg protein in the 100,000 g fraction and 790 in the 12,000 g pellet fraction. The specific activity of ethanol oxidation was 1590 nmoles acetaldehyde formed/min/mg protein in the 100,000 g fraction and 820 in the 12,000 g pellet fraction. The activity was enzymatic in that it was linear with time, proportional to protein concentration, and sensitive to temperature. Catalase appeared to be the enzymatic component responsible for the oxidation. In this ascorbate-dependent alcohol oxidation system, oxygen was consumed and H2O2 was formed. When purified catalase and ascorbate were used, complex I was detected and methanol was oxidized.

Hepatic progenitors and strategies for liver cell therapies.

Liver cell therapies, including liver cell transplantation and bioartificial livers, are being developed as alternatives to whole liver transplantation for some patients with severe liver dysfunction. Hepatic progenitors are proposed as ideal cells for use in these liver cell therapies given their ability to expand extensively, differentiate into all mature liver cells, have minimal immunogenicity, be cryopreservable, and reconstitute liver tissue when transplanted. We summarize our ongoing efforts to develop clinical programs of hepatic progenitor cell therapies with a focus on hepatic stem cell biology and strategies that have emerged in analyzing that biology.

Ascorbic acid and elevated SGOT levels after an acute dose of ethanol in the guinea pig.

Male guinea pigs were maintained on a vitamin C-deficient chow diet and supplemented with either 0.05 or 2.0 mg of ascorbic acid/ml drinking water for 3 weeks prior to receiving an intraperitoneal injection of 4.0 g of ethanol/kg body weight. The following biochemical parameters were measured prior to, and hourly for 12 hours after, ethanol administration: serum glutamic-oxaloacetic transaminase (SGOT), serum glutamic-pyruvate transaminase (SGPT), serum triglycerides, and blood ethanol clearance. The animals were killed 12 hours after ethanol administration and liver weight to body weight ratios and hepatic ascorbic acid concentrations determined. Acute ethanol administration resulted in a 12-fold increase in SGOT levels in animals with hepatic ascorbic acid concentrations at or below 16 mg/100 g of liver. A marked reduction, 60%, in this increase was observed in animals that had concentrations of hepatic ascorbic acid above 16 mg/100 g of liver. No effect of hepatic ascorbic acid concentration was observed on elevated levels of SGPT, serum triglycerides, or blood ethanol clearance.

Cataracts in dogs following subchronic administration of the phenylpiperazine antihypertensive agent PD 78787.

PD 78787, 3-[4-[4-(3-methylphenyl)-1-piperazinyl]butyl]-2,4-imidazolinedione, was an antihypertensive drug candidate with alpha 1 adrenoreceptor blockade identified as one of its pharmacologic activities. Beagle dogs were administered daily doses of 0, 1, 5, or 10 mg/kg for 41 weeks. During the study, periodic ophthalmic examinations were performed in addition to electrocardiography, blood pressure measurements, and hematological, clinical biochemical, and urinalysis assessments. At study termination, animals were euthanatized and the following procedures conducted; complete gross pathological examinations; histopathologic examination of lens; biochemical analysis of aqueous humor; and measurements of drug concentration in plasma, aqueous humor, and lens. Clinical signs observed included miosis, relaxed membrane nictitans, and somnolence. Ophthalmic examinations at Week 13 revealed unilateral posterior lenticular opacities at the dose of 10 mg/kg in two of four females. At Week 41, mature bilateral cataracts were observed in four of four females and three of four males administered the 10 mg/kg dose. The opacities appeared to develop from the posterior suture lines. No adverse effects on aqueous humor composition were observed. Significant concentrations of PD 78787 were found in lens and aqueous humor from all dose groups 24 hr following the last dose. These concentrations increased with increasing dose averaging 4 micrograms/ml in the lenses of dogs administered 10 mg/kg. Histopathologically, swelling, vacuolation, and dissolution of the lenticular fibers were observed at 10 mg/kg. All other study parameters were unaffected by drug treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex differences in rat hepatic cytolethality of the protein kinase C inhibitor safingol: role of biotransformation.

Safingol [(2S,3S)-2-amino-1,3-octadecanediol], a sphingosine analog that inhibits protein kinase C, was developed to treat dermatoses and cancer. Preclinical toxicology studies performed to assess the effects of safingol showed that 6 weeks of dermal application over 10% of body surface area caused dose-dependent increases in serum enzymes and hepatic histopathological changes associated with liver damage in female rats. Liver toxicity was not seen in male rats at the same doses. Plasma safingol concentrations were similar in male and female rats following topical exposure. The underlying mechanism(s) for the sex differences in toxicity in rats were examined using isolated hepatocytes. An in vitro model of male versus female differences in safingol.HCl-induced hepatotoxicity was established using a suspension/culture technique. Concentrations of safingol.HCl which produced cytolethality in 50% of the hepatocytes were 125 and 48 microM for male and female rat hepatocytes, respectively. Cytolethality was time-, concentration-, and cell number-dependent. Inhibition of cytochrome P450 in vitro with 1-phenylimidazole increased safingol.HCl-induced cytolethality in male but not female hepatocytes, suggesting that male rat hepatocytes have a cytochrome p450 isoenzyme which metabolizes safingol.HCl to an inactive metabolite thus reducing hepatotoxicity. Furthermore, in vivo pretreatment with the CYP4A-inducing agent, clofibrate, protected both male and female hepatocytes from cytolethality. The results of this study indicate that the sex differences seen in hepatotoxicity could be due to differences in biotransformation such that female rat hepatocytes either lack or have a reduced constitutive level of a cytochrome P450 isoenzyme that metabolizes safingol to a nontoxic metabolite. In addition, safingol produced hepatocyte cell death without inflammation in vivo, and a "ladder-like" DNA fragmentation pattern in vitro, consistent with an apoptotic mechanism of cell death.

Preclinical toxicological evaluation of fostriecin, a novel anticancer antibiotic, in rats.

Fostriecin, a novel anticancer antibiotic produced by Streptomyces pulveraecus, is believed to act via inhibition of topoisomerase II. Single-dose intravenous administration to rats at dose levels of 8.8 to 48 mg/kg resulted in lethality at dose levels of 35 mg/kg and higher. Major toxic effects were observed primarily at 17.5 mg/kg and higher, were reversible, and consisted of bone marrow hypocellularity, leukopenia, neutropenia, thrombocytopenia, and diffuse necrosis of various lymphoid tissues. The kidney was also identified as a target organ. Renal effects were observed primarily at 20 mg/kg, were reversible, and included increases in serum BUN, creatinine, and 24-hr glucose excretion. Twenty-four-hour excretion of Na+, K+ and urine osmolality were decreased postdosing at 10 and 20 mg/kg. Renal lesions, observed primarily at 20 mg/kg, consisted of vacuolization and necrosis of proximal and distal tubular epithelium at the corticomedullary junction extending into the medulla. Repeated daily intravenous administration of fostriecin for 5 days to rats at dose levels of 2.5 to 26.5 mg/kg resulted in death at 10 mg/kg and above and similar hematologic, bone marrow, lymphoid tissue, and renal changes as observed in the single-dose study. Hematological, bone marrow, lymphoid, and renal changes observed in rats were consistent with the cytotoxic mechanism of action of the compound.

Renal morphology and function in dogs after treatment with the angiotensin-converting enzyme inhibitor quinapril.

Angiotensin-converting enzyme (ACE) inhibitors have proven to be effective therapeutic agents for treatment of hypertension and congestive heart failure (CHF). Because of the role the renin-angiotensin system (RAS) plays in maintaining renal homeostasis, the effect these compounds have on renal function has been of interest. We assessed the effect of toxicologically significant doses of the new ACE inhibitor, quinapril, on renal function and morphology in dogs. Groups of 3 male beagle dogs were administered quinapril orally at daily doses of 0, 25, 125, or 250 mg/kg for 13 weeks. After treatment, animals were anesthetized and assessed for clinical pathologic and renal functional disturbances under normal conditions and after volume expansion and diuresis. Renal histopathology was conducted on perfusion-fixed kidney. No adverse effects on sensitive measures of renal function were detected; changes observed were consistent with the pharmacologic consequences of ACE inhibition. Decreased serum Na+ and Cl- (< 10%) and hematocrit at 125 and 250 mg/kg, twofold increases in serum creatinine and blood urea nitrogen (BUN) at 250 mg/kg, and decreased arterial blood pressure (BP) (20%) were observed at all doses. Under baseline conditions, urine flow increased 81-123% in quinapril-treated animals as compared with controls and urine specific gravities decreased 16% relative to controls at 125 and 250 mg/kg. Microscopically, juxtaglomerular hypertrophy was observed at all doses. At 250 mg/kg, minimal, widely scattered cortical tubular alterations were observed; glomerular lesions were not. No significant adverse effects of quinapril on renal morphology or function were observed at doses approximately 250 times the therapeutic dose.

Ascorbic acid chronic alcohol consumption in the guinea pig.

Protection against the toxic effects of chronic alcohol consumption was observed in male guinea pigs maintained on a high-ascorbic-acid diet (vitamin C-deficient chow plus 2.0 mg ascorbic acid/ml drinking water) as compared to animals on a low-ascorbic-acid diet (vitamin C-deficient chow and from 0.025 to 0.050 mg ascorbic acid/ml drinking water). Alcohol was orally administered to the guinea pigs at a dose of 2.5 g/kg for up to 14 weeks. Levels of serum aspartate aminotransferase and serum alanine aminotransferase were significantly elevated in animals on the low-ascorbic-acid diet that received alcohol, 120 and 250%, respectively. In contrast, in animals on the high-ascorbic-acid diet that received alcohol, levels of alanine aminotransferase were not significantly elevated and levels of aspartate aminotransferase were elevated 50%. In addition, some of the animals on the low-ascorbic-acid diet that received alcohol for 12 to 14 weeks developed hepatic steatosis and necrosis, whereas none of the animals on the high-ascorbic-acid diet that received alcohol for the same length of time manifested these changes.

Renal structure and function in rats after suprapharmacologic doses of quinapril, an angiotensin-converting enzyme inhibitor.

Angiotensin-converting enzyme (ACE) inhibitors have adverse effects on renal function in some hypertensive patients, and some of them produce renal tubular lesions in animals at high doses. To assess the effect of quinapril on renal function and structure, a 4-week time-course study was conducted in male Wistar rats with daily oral gavage doses of 0, 10, 100, or 400 mg/kg. Glomerular filtration rate (GFR) estimated as creatinine clearance and fractional electrolyte excretion values were derived from urinalysis and blood chemistry data obtained at days 1, 7, 14, and 28. Renal sections were collected on these days for histopathologic evaluation, and cortical slices were obtained to assess organic ion transport in vitro. Expected pharmacologic effects of an ACE inhibitor were observed at all doses and included increased urine output, increased water consumption, decreased serum aldosterone (65 or 25% of control at 10 or 400 mg/kg, respectively, on day 28), increased plasma renin activity (PRA, up to two- to threefold higher than controls at day 28), and hypertrophy of the juxtaglomerular apparatus. Despite these expected class effects, quinapril administration to male rats for 28 days produced no functional alterations or renal tubular lesions suggestive of renal toxicity at doses up to 400-fold higher than the effective antihypertensive dose in rats.

Toxicity of the protein kinase C inhibitor safingol administered alone and in combination with chemotherapeutic agents.

Safingol [(2S,3S)-2-amino-1,3-octadecanediol] potentiates the toxicity of doxorubicin (DOX) and cisplatin (CIS) against tumor cells in vitro and in vivo. The present studies were conducted in rats and dogs to evaluate safingol toxicity when administered i.v. as a single agent and to evaluate safingol's ability to potentiate the toxicity of established chemotherapeutic agents to normal tissues in vivo. In an escalating dose study, dogs were administered safingol i.v. at 5, 10, 20, 30, 40, and 75 mg/kg on Days 1 through 6. Necropsies were performed on Day 7. Red urine was observed at 10 mg/kg and higher. Icterus was observed following 40 mg/kg with additional signs of hypoactivity and anorexia occurring after 75 mg/kg. Clinical and microscopic pathology revealed marked hepatotoxicity, venous degeneration and necrosis at injection sites, and evidence of intravascular hemolysis. Doses of 5, 20, or 40 mg safingol/kg were utilized in single i.v. dose rat and dog studies. No evidence of adverse systemic toxicity was seen up to 20 mg/kg in either species [for rats: Cmax = 12,600 (males) or 17,133 (females) ng/ml, AUC = 3853 (males) or 4365 (females) ng x hr/ml; for dogs: Cmax = 2533 ng/ml, AUC = 2851 ng x hr/ml (no sex differences)]. Local effects of venous irritation or intravascular hemolysis were observed at all doses in rats and at 20 and 40 mg/kg in dogs. A dose of 40 mg/kg [for rats: Cmax = 31,233 (males) or 91,300 (females) ng/ml, AUC = 11,519 (males) or 18,620 (females) ng x hr/ml; for dogs: Cmax = 9033 ng/ml, AUC = 11,094 ng x hr/ml (combined sex)] was associated with clinical pathologic and renal histomorphologic changes considered consequent to intravascular hemolysis in both species, lethality and testicular toxicity in rats, and clinical biochemical changes indicative of hepatobiliary injury in dogs. Studies indicated that hemolysis occurred during infusion, was not caused by circulating levels of safingol, and was a function of dose concentration and vein of delivery. Safingol at 10 or 20 mg/kg was administered i.v. to rats 30-60 min prior to myelosuppressive i.v. doses of DOX, CIS, or cyclophosphamide (CYP). Hematology, plus renal function and morphology for CIS-treated animals, was assessed 4 and 14 days later.(ABSTRACT TRUNCATED AT 400 WORDS)