Effects of high dose ascorbate administration on L-10 tumor growth in guinea pigs

Sodium ascorbate is preferentially toxic to tumor cells at high concentrations. It has not been established, however, whether sufficient intra-tumor ascorbate concentrations are safely achievable in vivo. We administered sodium ascorbate subcutaneously or orally for eighteen days to Sewall-Wright strain-2 guinea pigs bearing intradermal L-10 hepatocarcinoma tumors. Tumor masses and intra-tumor ascorbate concentrations were determined at necropsy. L-10 cells formed tumors that metastasized to the lymph nodes, with tumor burdens reaching nearly 50 grams in untreated animals. Subcutaneous injections of ascorbate (500 mg/kg/day) inhibited tumor growth by as much as sixty-five percent, with oral supplementation reducing it by roughly fifty percent. Tumor growth correlated inversely with intra-tumor ascorbate concentration, the latter exceeding 2 mM in some cases. Ascorbate concentrations sufficient to kill tumor cells can be safely achieved in solid tumors in vivo, suggesting a possible role for high dose intravenous ascorbate in treating cancer.     

Pharmacokinetics of all-trans retinoyl beta-glucuronide in rats following intraperitoneal and oral administration

The purpose of this study was to examine the pharmacokinetics of a single dose (6.3 mumol, 3 mg) of all-trans retinoyl beta-glucuronide (RAG), when given either orally in corn oil or by intraperitoneal (i.p.) injection in dimethylsulfoxide (DMSO) to adult Sprague-Dawley rats. Following dosing, serial blood samples were collected at various times up to 48 hours from each rat via saphenous vein puncture. Retinoids were extracted from plasma samples and analyzed by high-performance liquid chromatography. In the plasma of i.p.-dosed rats (n = 6), a derivative of RAG, tentatively identified as the lactone of RAG (RAGL), was the major product found. RAGL persisted in the plasma for up to 48 hours. Much smaller concentrations of RAG and of retinoic acid (RA) were also present in the plasma at two to four hours, but generally not thereafter. In orally dosed rats (n = 6), neither RAG nor its products, except for occasional traces of the lactone, were detected. Plasma retinol levels decreased in both i.p.-injected and orally treated rats, the decrease being significant in orally dosed rats.     

In vivo vitamin C deficiency in guinea pigs increases ascorbate transporters in liver but not kidney and brain

Moderate vitamin C (vitC) deficiency (plasma concentrations less than 23 μmol/L) affects as much as 10% of adults in the Western World and has been associated with an increased mortality in disease complexes such as cardiovascular disease and the metabolic syndrome. The distribution of vitC within the body is subjected to complex and nonlinear pharmacokinetics and largely depends on the sodium-dependent vitC-specific transporters, sodium-dependent vitamin C transporter 1 (SVCT1) and sodium-dependent vitamin C transporter 2 (SVCT2). Although currently not established, it is likely to expect that a state of deficiency may affect the expression of these transporters to preserve vitC concentrations in specific target tissues. We hypothesized that diet-induced states of vitC deficiency lead to alterations in the messenger RNA (mRNA) and/or protein expression of vitC transporters, thereby regulating vitC tissue distribution. Using guinea pigs as a validated model, this study investigated the effects of a diet-induced vitC deficiency (100 mg vitC/kg feed) or depletion (0 mg vitC/kg feed) on the expression of transporters SVCT1 and SVCT2 in selected tissues and the transport from plasma to cerebrospinal fluid (CSF). In deficient animals, SVCT1 was increased in the liver, whereas a decreased SVCT1 expression but increased SVCT2 mRNA in livers of depleted animals suggests a shift in transporter expression as response to the diet. In CSF, a constant plasma:CSF ratio shows unaltered vitC transport irrespective of dietary regime. The study adds novel information to the complex regulation maintaining vitC homeostasis in vivo during states of deficiency.     

Modification of serum proteins in guinea pigs immunized and challenged with toluene diisocyanate

OBJECTIVES: Guinea pigs were used to determine whether immunization and challenge by toluene diisocyanate (TDI) induce changes in the serum protein concentrations of the "acute-phase response" and whether TDI can form adducts with serum proteins. METHODS: Guinea pigs were immunized by weekly intradermal injections of TDI and challenged with TDI 7 days after the 3rd injection. The animals were killed 6 hours after the challenge, and serum was analyzed for protein characterization by gel electrophoresis and for specific antibodies to TDI by enzyme-linked immunosorbent assay (ELISA) and Western blotting. RESULTS: The total serum protein concentration of the immunized TDI-challenged guinea pigs increased in comparison with that of nonimmunized animals [75 (SE 0.7) versus 47.4 (SE 2.3) mg/ml; ]. Albumin and alpha, and alpha2 globulins increased significantly [respectively: 65.8 (SE 0.2)%, 2.1 (SE 0.1)% and 7.2 (SE 0.1)% versus 59 (SE 1.3)%, 1.3 (SE 0.1)% and 3.7 (SE 0.1)%], whereas beta1 and beta2 globulins decreased in the immunized TDI-challenged guinea pigs [7.8 (SE 0.2)% and 0.8 (SE 0.2)% versus 15.8 (SE 0.7)% and 4.8 (SE 0.2)%]. The gamma globulin concentrations did not change significantly. In the immunized TDI-challenged animals, albumin was modified by TDI and ran faster on agarose gel electrophoresis than did albumin from nonimmunized guinea pigs. In the ELISA, only immunized animals had high titers of TDI-specific antibodies (IgG and IgG1); by blotting, the antibodies reacted against TDI, the TDI-BSA-conjugate and several TDI-conjugated guinea pig serum proteins, but they did not react against any native or denaturated serum protein when unconjugated with TDI. CONCLUSIONS: These findings indicate that, in guinea pigs, immunization and challenge with TDI induces changes in serum proteins of the "acute phase response" and TDI is adducted to serum proteins with different molecular weights (eg, albumin).     

Provocation of respiratory allergy in guinea pigs following inhalation of free toluene diisocyanate

An animal exposure experiment which simulated a workplace exposure situation was made to compare toluene diisocyanate (TDI) concentrations which resulted in antibody production with those which elicited pulmonary responses. Groups of guinea pigs were exposed to inhaled TDI from 0.02 to 1.0 ppm (g/g) for 3 h/day on 5 consecutive days. Three weeks later the animals were challenged with 0.02 ppm of free TDI for 15 min. TDI specific antibodies and pulmonary responses were evaluated. Specific antibody production showed a linear correlation to TDI concentration at induction. Most of the animals exposed to TDI levels above 0.2 ppm displayed significant pulmonary responses, but no correlation was found between TDI concentration at induction and the intensity of pulmonary response upon challenge to free TDI. These results indicated that there was a threshold concentration of 0.02 ppm TDI for antibody production and for the development of pulmonary response. It was also found that exposure to TDI at a level lower than its threshold concentration for sensitization may elicit a response in previously sensitized individuals.     

Effect of dietary ascorbic acid on levels of serum mineral nutrients in guinea pigs

The effect of dietary ascorbic acid on the serum mineral nutrients, Ca, Cu, Fe, K, Mg, Mn, Na and Zn in guinea pigs has been studied. Large amounts of ascorbic acid were administered to experimental animals in their drinking water. The daily ascorbic acid intake from the diet for the control animals was 10 mg/kg body weight. The mean ascorbic acid intakes for the two groups of experimental animals were 366 (37 times control) and 722 (72 times control) mg/kg body weight/day. In the ascorbic acid-treated animals, there was a significant increase in serum ascorbic acid levels in comparison with the controls. No substantial differences were observed in the body weights. The large quantities of dietary ascorbic acid did not influence serum levels of all eight minerals studied when the experimental and control values were compared using the two-tailed Student's t-test. However, serum level of copper in the guinea pigs ingesting a daily dose of 722 mg of ascorbic acid per kg body weight was slightly below control value when one-tailed Student's t-test was used.     

Toxicity and tissue levels in the rat and guinea pig following acute hexachlorobenzene administration

Summary DDT injected intraperitoneally into black surfperch caused substantial increases in plasma osmotic concentration only at doses much larger than are likely to be encountered in nature. Increased plasma concentrations were below those tolerated by fish adapted to high salinities. Death of marine teleosts from DDT poisoning probably involves factors other than simply osmoregulatory failure.     

Radioimmunoassay of serum d-norgestrel in women following oral and intravaginal administration.

Serum level of dl-norgestrel (dl-Ng) were measured by a special radioimmunoassay method after oral and intravaginal administration. 3 women received .075 mg/day dl-Ng orally for 5 days, and 3 others received 50 or 100 mg dl-Ng via a polysiloxane elastomer placed in the vagina for 3 weeks. The radioimmunoassay method proved to be highly effective; cross reacting with less than .01% 1-Ng. Circulating levels of dl-Ng were detectable 30 minutes after oral ingestion, and reached peak values of 2, 1.7 and 1.5 ng/ml in 1 and 2-3 hours, respectively. Serum levels fell rapidly thereafter, reaching levels of .2-.4 ng/ml within 24 hours after injection. Serum dl-Ng levels rose rapidly after insertion of the intravaginal device, and reached peak values of 5 ng/ml and 7-11 ng/ml with 50 and 100 mg dl-Ng, respectively, within 24-48 hours after insertion. Serum dl-Ng levels then declined to about 30-40% of initial treatment concentrations. During subsequent cycles, serum dl-Ng levels remained relatively constant at 1-3 ng/ml. Concentrations declined rapidly to .2 ng/ml within 5-7 days after removal of the device. Preovulatory patterns of estradiol were observed, but ovulation did not occur, as evidenced by low progesterone values. During the 1st and 2nd treatment cycles, withdrawal bleeding began at times ranging from the day of removal to 5 days after removal. In the later treatment cycles, withdrawal bleeding began prior to removal of the device. The results indicate that the more constant release of dl-Ng with the intravaginal ring provides better control of irregular bleeding than orally administered dl-Ng.     

A comparison of ethanol absorption and narcosis in long- and short-sleep mice following intraperitoneal or intragastric ethanol administration

Blood ethanol concentrations (BEC) were determined in Long-Sleep (LS) and Short-Sleep (SS) mice during a 30 min period following ethanol (ETOH) administration. Absorption of ETOH was rapid and followed a similar time course in the two lines after intraperitoneal (IP) administration of 3.8 or 4.5 g/kg. Following intragastric (IG) administration, slower absorption and lower peak BECs were noted in both lines, but in LS mice this effect was more pronounced. The two routes of administration were not effective in altering duration of loss of the righting reflex (LRR), or waking BECs following 4.5 g/kg ETOH. LS mice had the expected longer LRR durations and lower BECs at waking than did SS mice. Differences in absorption rate and peak BEC are concluded to be unrelated to ETOH neurosensitivity in these mice.