Emodin-induced hepatotoxicity was exacerbated by probenecid through inhibiting UGTs and MRP2

Aggravating effect of probenecid (a traditional anti-gout agent) on emodin-induced hepatotoxicity was evaluated in this study. 33.3% rats died in combination group, while no death was observed in rats treated with emodin alone or probenecid alone, indicating that emodin-induced (150 mg/kg) hepatotoxicity was exacerbated by probenecid (100 mg/kg). In toxicokinetics-toxicodynamics (TK-TD) study, aspartate aminotransferase (AST) and systemic exposure (area under the serum concentration-time curve, AUC) of emodin and its glucuronide were significantly increased in rats after co-administrated with emodin and probenecid for 28 consecutive days. Results showed that the increased AUC (increased by 85.9%) of emodin was mainly caused by the decreased enzyme activity of UDP-glucuronosyltransferases (UGTs, decreased by 11.8%-58.1%). In addition, AUC of emodin glucuronide was increased 5-fold, which was attributed to the decrease of multidrug-resistant-protein 2 (MRP2) protein levels (decreased by 54.4%). Similarly, in vitro experiments proved that probenecid reduced the cell viability of emodin-treated HepG2 cells through inhibiting UGT1A9, UGT2B7 and MRP2. Our findings demonstrated that emodin-induced hepatoxicity was exacerbated by probenecid through inhibition of UGTs and MRP2 in vivo and in vitro, indicating that gout patients should avoid taking emodin-containing preparations in combination with probenecid for a long time.

[Serious risk related to oral use of sodium phosphate solution]

Sodium phosphate solutions are commonly used to cleanse the bowel in preparation for colonoscopy, for barium enema or surgical procedures and eventually for treatment of severe constipation. Though relatively safe, these drugs must be used with caution in patients with kidney disease, small intestinal disorders, or poor gut motility and are prohibited in renal insufficiency and bowel obstruction. Especially elderly patients are at increased risk for phosphate intoxication due to decreased glomerular filtration rate, concomitant medication use, and systemic and gastrointestinal diseases. Sodium phosphate solution could induce by at-risk patients serious electrolyte abnormalities (hyperphosphatemia, hypocalcemia, hypokalemia) and acute kidney injury called acute phosphate nephropathy, which is potentially life-threatening condition with slowly progressive renal insufficiency. This article gives a report on two cases of severe adverse effects after administration of oral sodium phosphate solution: an elderly women who developed increase in serum phosphate with compensatory severe hypokalcemia with tetany; and an elderly man who developed acute phosphate nephropathy following colon preparation prior to colonoscopy and barium enema. Especially in elderly and in patients in whom sodium phosphate solution is contraindicated or should be used with caution, we recommend to use isosmotic macrogol (polyethylene glycol) solution for the bowel cleansing a for the treatment of constipation.

Bioenergetic effects of sodium sulfate on the freshwater crustacean, Ceriodaphnia dubia

I tested the hypothesis that if sodium sulfate alters the bioenergetics of Ceriodaphnia dubia, concentrations that cause reduced fecundity in the short (7-day) and long (5 generations) term should also cause changes in feeding rate and/or metabolism, measured as oxygen consumption. In addition, to test the hypothesis that an altered bioenergetic level caused by sodium sulfate exposure will affect the response of that organism to another toxicant, I measured the acute toxicity of phenol to C. dubia in the presence and absence of both food and sodium sulfate. Sodium sulfate reduced the filter-feeding rate of C. dubia, which was associated with significantly reduced oxygen consumption. This decreased energy level appeared to result in a consistent but decreased level of fecundity over a number of generations and the reproductive impairment was dose-dependent. These effects occurred at concentrations much lower than those at which acute (mortality) effects have been observed, a finding that may have regulatory implications. In addition, whereas phenol toxicity to C. dubia was exacerbated by the addition of food, increased phenol toxicity, likely induced by an increase in filtering or metabolic rate due to food addition, was negated when sodium sulfate was added to the test medium.

Phenolphthalein and Bisacodyl: Assessment of Genotoxic and Carcinogenic Responses in Heterozygous p53 (+/−) Mice and Syrian Hamster Embryo (SHE) Assay

Phenolphthalein (800 and 2400 mg/kg/day by gavage and 2400 mg/kg/day by diet) and bisacodyl (800-500, 4000-2000, and 8000 mg/kg/day by gavage) were administered to 15 male and 15 female and 20 male and 20 female p53(+/-) mice respectively for 26 weeks to investigate the potential carcinogenicity of each compound. Toxicokinetic analyses confirmed systemic exposure. p-Cresidine was administered by gavage (400 mg/kg/day) and served as the positive control agent in each study. Dietary phenolphthalein reduced survival in both sexes and early deaths were attributed to thymic lymphoma. No bisacodyl-related neoplasms were observed. Regardless of route of administration to p53(+/-) mice, phenolphthalein but not bisacodyl was unequivocally genotoxic, causing increased micronuclei in polychromatic erythrocytes. In the Syrian hamster embryo (SHE) cell transformation assay, phenolphthalein caused increases in morphologically transformed colonies, thereby corroborating NTP's earlier reports, showing phenolophthalein has potential carcinogenic activity. Bisacodyl was negative in the SHE assay. Results of these experiments confirm an earlier demonstration that dietary phenolphthalein causes thymic lymphoma in p53(+/-) mice and show that (1) phenolphthalein causes qualitatively identical results in this transgenic model regardless of route of oral administration, (2) phenolphthalein shows evidence of micronucleus induction in p53(+/-) mice for up to 26 weeks, (3) phenolphthalein induced transformations in the in vitro SHE assay, and (4) bisacodyl in p53(+/-) mice induces neither drug-related neoplasm, nor micronuclei in polychromatic erythrocytes, and did not induce transformations in the in vitro SHE assay.

An oral carcinogenicity and toxicity study of senna (Tinnevelly senna fruits) in the rat

Senna (Tinnevelly senna fruits), a known laxative derived from plants, was administered by gavage to Sprague-Dawley (Crl:CD (SD) BR) rats once daily at dose levels of 0, 25, 100 and 300 mg/kg/day for up to 104 consecutive weeks. Based upon clinical signs related to the laxation effect of senna, the highest dose (300 mg/kg/day) was considered to be a maximum tolerated dose. Sixty animals per sex were assigned to the control and dose groups. Assessments included clinical chemistry, hematology, full histology (control and high-dose groups; in addition, low and mid dose: intestinal tract, adrenals, liver, kidneys, brain and gross lesions) and toxicokinetics. The primary treatment-related clinical observation was mucoid feces seen at 300 mg/kg/day. When compared to controls, animals administered 300 mg/kg/day had slightly reduced body weights, increased water consumption and notable changes in electrolytes in serum (increases in potassium and chloride) and urine (decreases in sodium, potassium and chloride). The changes in electrolytes are most likely physiologic adaptations to the laxative effect of senna. At necropsy, dark discoloration of the kidneys was observed in animals in all treated groups. Histological changes were seen in the kidneys of animals from all treated groups and included slight to moderate tubular basophilia and tubular pigment deposits. In addition, for all treated groups, minimal to slight hyperplasia was evident in the colon and cecum. These histological changes, together with the changes seen in the evaluation of clinical chemistry and urine parameters, have been shown to be reversible in a previous 13-week rat study of senna. No treatment-related neoplastic changes were observed in any of the examined organs. Based upon these data, it is concluded that senna is not carcinogenic even after daily administration for 2 years at dosages of up to 300 mg/kg/day in Sprague-Dawley rats.

Spasmogenic activity and acute toxicity of Yumijangquebo, a herbal laxative formulation

We evaluated the pharmacological properties and spasmogenic activities of Yumijangquebotrade mark, a Korean herbal laxative formulation. Doses in the range 12-50 microg/ml induced a large spasmogenic effect in isolated guinea pig ileum, similar to that induced by acetylcholine. Pre-treating the tissue with atropine (0.2 microM) completely abolished the contractile effect of Yumijangquebo. The spasmogenic effect of Yumijangquebo and the inhibition of this effect by atropine suggest that a cholinergic mechanism is responsible for its effects. Yumijangquebo increased the gastrointestinal motility in ICR mice at doses between 10 and 37 mg/kg. Yumijangquebo exhibited higher activity than three other laxatives tested, which had activities about 85% of that of Yumijangquebo. In an acute toxicity study using Sprague-Dawley rats, the median lethal dose (LD50) of Yumijangquebo was greater than 2000 mg/kg, and we found no pathological changes in macroscopic examination by necropsy of rats treated with Yumijangquebo. We conclude that Yumijangquebo may be safely used as a herbal spasmogenic laxative agent.

A 13-week oral toxicity study of senna in the rat with an 8-week recovery period

Senna was administered by gavage to Sprague Dawley rats once daily at dose levels of 0, 100, 300, 750 or 1500 mg/kg for up to 13 consecutive weeks followed by an 8-week recovery period for selected animals. Dose- and treatment-related clinical signs included abnormal feces, which were seen to varying degrees from animals at 300 mg/kg per day and more. Animals receiving 750 or 1500 mg/kg per day had significantly reduced body weight gain (males only) and, related to the laxative properties of senna, increased water consumption and notable changes in electrolytes in both serum and urine. At both the terminal and recovery phase necropsy, an increase in absolute and relative kidney weights was seen for male and female animals receiving 750 and/or 1500 mg/kg per day. A dark discoloration of the kidneys was observed at necropsy along with histopathological changes in the kidneys (slight to moderate tubular basophilia and pigment deposits) at 300 mg/kg and above. However, there were no indications in laboratory parameters of any renal dysfunction. In addition, for all treated groups, minimal to slight hyperplasia was recorded in the forestomach and large intestine. Following 8 weeks of recovery, with the exception of the brown pigment in the kidneys, there were no histopathological abnormalities. Thus, the biochemical and morphological changes seen following 13 weeks of treatment of senna significantly reversed following 8 weeks of recovery.

Biodynamic constituents in the Mexican morning glories: purgative remedies transcending boundaries

Jalap, a pre-Hispanic herbal remedy still considered a useful laxative, is an ingredient in some over-the-counter products sold by herbalists in contemporary Mexico. The purgative crude drugs are prepared from the roots of several morning glories species which all have been identified as members of the Ipomoea genus (Convolvulaceae). Their incorporation as therapeutical agents into Europe is an outstanding example of the assimilation of botanical drugs from the Americas as substitutes for traditional Old World remedies. Phytochemical investigations on the resin glycosides, main constituents of these drugs, were initiated during the second half of the XIX century; however, the structures of their active ingredients had remained poorly known, and still are for some members of these purgative root species. Modern analytical techniques with higher resolution capabilities (HPLC) for the isolation of the active principles of these crude drugs used in conjunction with powerful spectroscopic methods (high field NMR) have facilitated the investigation of these relevant, to the herbal product market, convolvulaceous species during the last decade. The advantages and limitations of theses techniques will be discussed. This review will also describe the ethnobotanical information associated with the Mexican morning glory species and how the traditional usages of these plants have played an important role in the selection of these materials for chemical studies. Little is as yet known about either the mechanism of purge action caused by the resin glycosides or the ecological significance of these same compounds for the producing plants. Over the five centuries of Mexican herbal medicine, one hundred years of phytochemistry has only partially elucidated the active ingredients of the jalap roots but has exemplified how to further contemporary drug discoveries through the investigation of those plants traditionally held to be economically and medicinally important in developing countries.

Acute toxicity and mutagenicity study on branched corn syrup and evaluation of its laxative effect in humans

We developed a branched corn syrup (BCS, average molecular weight: 500, content of indigestible portion: 45%) by heat treatment of indigestible dextrin with hydrochloric acid. To confirm the safety of BCS, we conducted both an acute toxicity test and a mutagenicity test. Moreover, we observed gastroenteric effects of BCS in fifty healthy humans. The results are summarized as follows. 1) There was no death observed after oral administration of BCS in Sprague-Dawley-strain rats. Lethal dose (LD)50, value was estimated to be more than 10 g/kg body weight. 2) No mutagenicity was observed in Salmonella typhimurium TA98, TA100, TA1535, TA1537, or Escherichia coli WP2uvrA. 3) Fifty adults were divided into five groups often (five of each sex) and orally administered BCS at 0.2, 0.3, 0.4. 0.5 and 0.6 g/kg body weight as indigestible portion. Although no diarrhea was observed in females, BCS at 0.6 g/kg as indigestible portion caused diarrhea in two out of five males. The maximum non-effective dose of indigestible portion of BCS was estimated to be 0.5 g/kg in males and more than 0.6 g/kg in females.

Induction of chromosome aberrations in vitro by phenolphthalein: mechanistic studies

Phenolphthalein induces tumors in rodents but because it is negative in assays for mutation in Salmonella and in mammalian cells, for DNA adducts and for DNA strand breaks, its primary mechanism does not seem to be DNA damage. Chromosome aberration (Ab) induction by phenolphthalein in vitro is associated with marked cytotoxicity. At very high doses, phenolphthalein induces weak increases in micronuclei (MN) in mouse bone marrow; a larger response is seen with chronic treatment. All this suggests genotoxicity is a secondary effect that may not occur at lower doses. In heterozygous TSG-p53((R)) mice, phenolphthalein induces lymphomas and also MN, many with kinetochores (K), implying chromosome loss. Induction of aneuploidy would be compatible with the loss of the normal p53 gene seen in the lymphomas. Here we address some of the postulated mechanisms of genotoxicity in vitro, including metabolic activation, inhibition of thymidylate synthetase, cytotoxicity, oxidative stress, DNA damage and aneuploidy. We show clearly that phenolphthalein does not require metabolic activation by S9 to induce Abs. Inhibition of thymidylate synthetase is an unlikely mechanism, since thymidine did not prevent Ab induction by phenolphthalein. Phenolphthalein dramatically inhibited DNA synthesis, in common with many non-DNA reactive chemicals that induce Abs at cytotoxic doses. Phenolphthalein strongly enhances levels of intracellular oxygen radicals (ROS). The radical scavenger DMSO suppresses phenolphthalein-induced toxicity and Abs whereas H(2)O(2) potentiates them, suggesting a role for peroxidative activation. Phenolphthalein did not produce DNA strand breaks in rat hepatocytes or DNA adducts in Chinese hamster ovary (CHO) cells. All the evidence points to an indirect mechanism for Abs that is unlikely to operate at low doses of phenolphthalein. We also found that phenolphthalein induces mitotic abnormalities and MN with kinetochores in vitro. These are also enhanced by H(2)O(2) and suppressed by DMSO. Our findings suggest that induction of Abs in vitro is a high-dose effect in oxidatively stressed cells and may thus have a threshold. There may be more than one mechanism operating in vitro and in vivo, possibly indirect genotoxicity at high doses and also chromosome loss, both of which would likely have a threshold.

Mitochondrial metabolism impairment in muscle fibres of rats chronically intoxicated with Senna occidentalis seeds

The chronic administration of S. occidentalis seeds was found to induce a mitochondrial myopathy in hens. This study was undertaken to determine if the chronic treatment with S. occidentalis seeds of rats (as a mammalian model) would induce a mitochondrial myopathy similar to those described in humans and to determine if the histological changes could be correlated with the amount of ingested seeds. Twenty-one days old rats were fed S. occidentalis seeds at different diet concentrations (1, 2, 3%). Rats fed 1% S. occidentalis seeds had only a few COX-negative muscle fibers in the pectoralis major muscle. Rats fed 3% Senna occidentalis seeds had a greater number of COX-negative fibers. Rats fed 2% had an intermediate number of COX-negative fibers. Activity of SDH and NADH-tr were decreased in rats of groups 2% and 3%. Our data indicate that a progressive mitochondrial metabolism impairment can be produced in rats fed S. occidentalis seeds and that this impairment can be correlated with the amount of ingested seeds.

Toxicity of commonly used laxatives

Laxatives have a particularly marked abuse potential. Since they are available without prescription, physicians have no influence whatsoever on frequency of intake and dosage. The stimulant laxatives are preferentially abused since they are particularly cheap and the nature of their effect makes them appear suitable to users for non-intended purposes; advertising sometimes reinforces such impressions. Stimulants of plant and chemical origin can certainly be regarded as aggressive chemical substances that are pharmacologically active. Available data suggest that it would be advisable to bring the use of these substances under medical supervision since their widespread abuse and the associated risks can only be substantially reduced by such action. This review summarises toxicological data of stimulant laxatives and other freely available but more safe compounds such as lactulose.

Prohibition of phenolphthalein

Welcome disappearance of phenolphthalein from medicinal use.

Phenolphthalein metabolite inhibits catechol-O-methyltransferase-mediated metabolism of catechol estrogens: a possible mechanism for carcinogenicity

Phenolphthalein (PT), used in over-the-counter laxatives, has recently been identified as a multisite carcinogen in rodents, but the molecular species responsible for the carcinogenicity is not known. A catechol metabolite of PT, hydroxyphenolphthalein (PT-CAT), was recently identified and may be the molecular species responsible for at least part of the toxicity/carcinogenicity of PT. We hypothesize that PT-CAT inhibits the enzyme catechol-O-methyltransferase (COMT) and therefore potentiates genotoxicity by either PT-CAT itself or the endogenous catechol estrogens (CEs) in susceptible tissues. The present studies were conducted to determine the effects of PT treatment and PT-CAT itself on the COMT-mediated metabolism of 4- and 2-hydroxyestradiol both in vitro and in vivo. Female mice were treated with PT (50 mg/kg/d) for 21 days and then euthanized. PT-CAT concentration in urine reached plateau levels by 7 days of exposure. An O-methylated metabolite of PT-CAT was detected in feces. In vitro experiments demonstrated that PT treatment resulted in an increase in free CEs, which are normally cleared by COMT and a concurrent decrease in the capacity of hepatic catechol clearance by COMT. In vitro, PT-CAT was a substrate of COMT, with kinetic properties within the range measured with endogenous substrates. PT-CAT was an extremely potent mixed-type inhibitor of the O-methylation of the catechol estrogens, with 90-300 nM IC50s. The above data, when taken together, suggest that chronic administration of PT may enhance metabolic redox cycling of both PT-CAT and the catechol estrogens and this, in turn, may contribute to PT-induced tumorigenesis.

Phenolphthalein induces chromosome aberrations in human and Chinese hamster liver cells (CHEL) cultured in vitro

Phenolphthalein is a nonprescription laxative agent that has been widely used during this century. Recent studies in animal models have shown that phenolphthalein has carcinogenic activity. In order to assess cytogenetic effects on human cells in vitro, we tested phenolphthalein in a chromosome aberration assay in human embryo cells derived from amniotic fluid. Our results show that phenolphthalein induces a significant increase in the frequency of chromosome aberrations in human cells. The lowest dose level at which the clastogenic effect is evident is 23.2 microg/ml. Similar positive results were obtained in a Chinese hamster liver cell line, which is metabolically competent to activate different classes of promutagens and procarcinogens into biologically active metabolites. Instead, parallel experiments in Chinese hamster ovary cells did not show any clastogenic effect due to phenolphthalein. These latter data suggested that phenolphthalein acts as a promutagen and must be metabolically activated to exert its clastogenic effect. Teratogenesis Carcinog. Mutagen. 20:209-217, 2000.

Does senna extract promote growth of aberrant crypt foci and malignant tumors in rat colon?

Current evidence suggests that aberrant crypt foci (ACF) can be used to evaluate agents for their potential colon carcinogenic activity. The aim of the present study was to determine whether senna pod extract (SE) itself induces ACF and tumors in the rat colon or increases the development of ACF and tumors induced by azoxymethane (AOM). A daily administration of SE 10 mg/kg by mouth for 13-28 weeks produced a weak laxative effect but did not itself cause the appearance of ACF or tumors. The numbers of ACF and tumors induced by AOM were, however, increased by a dose of SE (100 mg/kg) able to induce chronic diarrhea over three months. These results suggest that SE does not cause the appearance of ACF or tumors in the rat colon nor does it have a promoting effect when given to rats at a dose that produces laxation (10 mg/kg), whereas a diarrhogenic dose (100 mg/kg) increases the appearance of tumors induced by AOM.

No clastogenic activity of a senna extract in the mouse micronucleus assay

In previous studies, an analytically well-defined senna extract, commonly used as a laxative, gave positive responses in vitro in the Ames test and in the CHO assay. Therefore, the objective of this study was to investigate the genotoxic activity of the same senna extract in an in vivo genotoxicity assay by means of the generally acknowledged MNT. After administration of an oral dose of 2000 mg senna extract/kg to NMRI mice of both genders, which is equivalent to 119 mg potential rhein/kg, 5.74 mg potential aloeemodin/kg and 0. 28 mg potential emodin/kg, there were no elevated levels of micronuclei in bone marrow cells. Kinetic studies were performed in parallel to demonstrate target organ availability. Highest concentrations in the plasma were reached after 1 h with 3.4 microg rhein/ml and 0.065 microg aloeemodin/ml. In all cases, emodin was below the limit of quantification. From the results, the in vitro clastogenic activity of the senna extract could not be confirmed in the mouse micronucleus assay. Together with further negative in vivo genotoxicity studies with anthranoids, the conclusion can be drawn that there is no indication so far demonstrating a genotoxic risk for patients taking senna laxatives.

Occurrence of emodin, chrysophanol and physcion in vegetables, herbs and liquors. Genotoxicity and anti-genotoxicity of the anthraquinones and of the whole plants

1,8-Dihydroxyanthraquinones, present in laxatives, fungi imperfecti, Chinese herbs and possibly vegetables, are in debate as human carcinogens. We screened a variety of vegetables (cabbage lettuce, beans, peas), some herbs and herbal-flavoured liquors for their content of the 'free' anthraquinones emodin, chrysophanol and physcion. For qualitative and quantitative analysis, reversed-phase HPLC (RP-LC), gas chromatography-mass spectrometry (GC-MS) and RP-LC-MS were used. The vegetables showed a large batch-to-batch variability, from 0.04 to 3.6, 5.9 and 36 mg total anthraquinone per kg fresh weight in peas, cabbage lettuce, and beans, respectively. Physcion predominated in all vegetables. In the herbs grape vine leaves, couch grass root and plantain herb, anthraquinones were above the limit of detection. Contents ranged below 1 mg/kg (dry weight). All three anthraquinones were also found in seven of 11 herbal-flavoured liquors, in a range of 0.05 mg/kg to 7.6 mg/kg. The genotoxicity of the analysed anthraquinones was investigated in the comet assay, the micronucleus test and the mutation assay in mouse lymphoma L5178Y tk+/- cells. Emodin was genotoxic, whereas chrysophanol and physcion showed no effects. Complete vegetable extract on its own did not show any effect in the micronucleus test. A lettuce extract completely abolished the induction of micronuclei by the genotoxic anthraquinone danthron. Taking into consideration the measured concentrations of anthraquinones, estimated daily intakes, the genotoxic potency, as well as protective effects of the food matrix, the analysed constituents do not represent a high priority genotoxic risk in a balanced human diet.

Final rule

The Food and Drug Administration (FDA) is issuing a final rule establishing that the over-the-counter (OTC) stimulant laxative ingredients danthron and phenolphthalein are not generally recognized as safe and effective and are misbranded. FDA is issuing this final rule as part of its ongoing review of OTC drug products after considering data and information on the safety of danthron and phenolphthalein.

Genotoxicity of sennosides on the bone marrow cells of mice

Preparations of a number of plants which contain hydroxyanthraquinones as active constituents are used worldwide for their laxative effect. Anthraquinone glycosides of Cassia angustifolia and C. fistula were investigated for their ability to induce a clastogenic effect on the bone marrow cells of Swiss albino mice. The endpoints screened were chromosomal aberrations and frequency of aberrant cells. Oral exposure to doses of these anthraquinones and their equivalent amount in leaf and pod extracts did not induce significant numbers of chromosomal aberrations or aberrant cells. The results indicate that anthraquinone sennoside B and rhein are weakly genotoxic.

Experimental study of antidiarrheal activity of Salicairine

Experimental antidiarrheal activity of a traditionally used medication, Salicairine, was demonstrated in comparison to loperamide by significant inhibition of castor oil-induced diarrhea in mice (increases in hard faeces/total faeces ratio of 38 and 54 and 5 and 54% with respect to controls, at 0.5 and 1 mL/kg and 1 and 2 mg/kg, respectively) and bisacodyl-induced increase in large intestine transit in rats (125 and 280 and 210% with respect to controls, at 0.4 and 2 mL/kg Salicairine and 5 mg/kg loperamide, respectively). Salicairine was able to reduce contractions of isolated rat duodenum induced by barium chloride and acetylcholine, although not completely (that is about 60%) as seen with loperamide. Also, it did not change normal gastrointestinal transit in mice at doses of 0.5 to 1 mL/kg, conversely to loperamide which had a significant effect (decrease of 50%) at 2 mg/kg. Finally, Salicairine at 0.01 mL/mL, like loperamide at 0.2 mg/mL, significantly increased net fluid absorption in rat colon, either in basal conditions (30 and 64% respectively) or after a prostaglandin E1-induced increase in net fluid secretion (41 and 35%, respectively). The antidiarrheal activity of Salicairine is possibly related, at least in part, to an increase in colon net fluid absorption or a decrease in net fluid secretion.

Cell-transforming activity and genotoxicity of phenolphthalein in cultured Syrian hamster embryo cells

Phenolphthalein is a cathartic agent widely used in non-prescription laxatives. For the simultaneous assessment of in vitro carcinogenicity and mutagenicity of phenolphthalein, the ability of this chemical to induce cell transformation and genetic effects was examined using the Syrian hamster embryo (SHE) cell model. Cell growth was reduced by treatment with phenolphthalein at 10-40 microM in a dose-related manner. Treatment with phenolphthalein for 48 hr induced a dose-dependent increase in morphological transformation of SHE cells. Over the dose range that resulted in cell transformation ( 10-40 microM), treatment of SHE cells with phenolphthalein induced gene mutations at the hprt locus but not at the Na+/K+ ATPase locus. A statistically significant level of chromosomal aberrations was elicited in SHE cells treated with phenolphthalein at the highest dose (40 microM). Meanwhile, neither numerical chromosomal changes nor DNA adduct formation, analyzed by the nuclease P1 enhancement version of 32P-post-labeling, were induced by treatment with phenolphthalein at any concentrations examined. We thus report cell-transforming activity and mutagenicity of phenolphthalein assessed with the same mammalian cells in culture. Our results provide evidence that phenolphthalein has cell-transforming and genotoxic activity in cultured mammalian cells. The mutagenic and clastogenic activities of phenolphthalein could be a causal mechanism for carcinogenicity in rodents.

Lack of emodin genotoxicity in the mouse micronucleus assay

The study was performed to investigate the potential of emodin (1,3,8-trihydroxy-6-methylanthraquinone) to induce micronuclei in polychromatic erythrocytes (PCEs). Mice of both genders received a single oral dose of 2000 mg emodin/kg and were killed 24 and 48 h later. Bone marrow cells were collected from 5 males and 5 females and 2000 PCEs per animal were scored for the presence of micronuclei. There was no enhancement in the frequency of micronuclei at both preparation intervals when compared to the negative controls. Blood level examinations confirmed the systemic availability of emodin. Plasma levels of up to 190 micrograms emodin/ml represented concentrations being in the concentration range that induced positive responses in several genotoxicity cell culture assays.

The role of constitutive and inducible nitric oxide synthase in senna- and cascara-induced diarrhoea in the rat

The role of constitutive and inducible nitric oxide (NO) synthase in rats treated with senna and cascara was studied. Senna (60 mg/kg p.o.) and cascara (800 mg/kg p.o.) ex vivo significantly increased Ca(2+)-dependent constitutive NO synthase activity in the rat colon. Induction of NO synthase (12% of the total NO synthase) was associated with cascara, but not senna, administration. Dexamethasone (0.03-0.3 mg/kg i.p.), which inhibits the expression of inducible NO synthase, significantly and dose-dependently reduced cascara-(but not senna-) induced diarrhoea and colonic fluid secretion. These findings suggest that senna probably exerts its laxative effect through stimulation of the constitutive isoform of NO synthase, while the inducible isoform of NO synthase also seems to be involved in the laxative effect of cascara.

Salinity tolerances of selected macroinvertebrates of the Sabie River, Kruger National Park, South Africa

Salinization has been identified as the most important problem facing the managers of South African freshwaters. Laboratory-based toxicity tests were conducted to assess the tolerance of selected macroinvertebrates to elevated salt concentrations. Since the Kruger National Park is the focus of river research in South Africa, and the Sabie River is the least mineralized river in the park, 96-h acute toxicity tests were conducted using Sabie River water and an ephemeropteran mayfly Tricorythus sp. found in the river. Experiments were conducted inflowing water systems known as raceways. The tolerance of the mayfly to two sodium salts, sodium chloride and sodium sulphate, was assessed at a range of selected conductivity levels/concentrations. The results indicated that mortality cannot be linked only to conductivity or total dissolved solid(TDS) concentrations, but also to the nature of the salt. Sodium sulphate was considerably more toxic to Tricorythus sp. than sodium chloride. Causes of mortality and implications for the development of water quality guidelines for the natural aquatic environment are discussed.

Genotoxicity of the laxative drug components emodin, aloe-emodin and danthron in mammalian cells: topoisomerase II mediated?

1,8-Dihydroxyanthraquinones are under debate as plant-derived carcinogens that are found in laxatives, food colors, and possibly vegetables. Published genotoxicity data are controversial, and so three of them (emodin, danthron and aloe-emodin) were tested in a number of in vitro assay systems. All three compounds induced tk-mutations in mouse lymphoma L5178Y cells. Induction of micronuclei also occurred in the same cell line, and was dose-dependent, with the potency ranking being danthron > aloe-emodin > emodin. In a DNA decatenation assay with a network of mitochondrial DNA of C. fasciulata, all three test compounds inhibited the topoisomerase II-mediated decatenation. Danthron and aloe-emodin, but not emodin, increased the fraction of DNA moving into comet tails when tested at concentrations around 50 microM in single-cell gel-electrophoresis assays (SCGE; comet assay). Comet assays were also used in modified form to determine whether pretreatment of the cells with the test compounds would reduce the effects of etoposide, a potent topoisomerase II inhibitor. All three test chemicals were effective in this pretreatment protocol, with danthron again being the most potent. Given clearcut evidence of their genotoxic activity, further research on the human cancer risk of these compounds may be warranted.

Phenolphthalein exposure causes multiple carcinogenic effects in experimental model systems

Phenolphthalein (a triphenylmethane derivative) has been commonly used as a laxative for most of the twentieth century, but little is known about its long-term carcinogenic potential in experimental studies. In our studies, phenolphthalein administered continuously in the feed for 2 years to F344 rats at doses of 0, 12,500, 25,000, and 50,000 ppm and to C57BL/6 x CH3 F1 (hereafter called B6C3F1) mice at doses of 0, 3,000, 6,000, and 12,000 ppm caused multiple carcinogenic effects. Treatment-related neoplasms occurred in the kidney and adrenal medulla in male rats, adrenal medulla in female rats, hematopoietic system in male and female mice (histiocytic sarcomas and malignant lymphomas), and ovary of female mice. Phenolphthalein has been shown to have estrogenic and clastogenic properties. Previous studies of other estrogenic chemicals (e.g., zearalenone) in the F344 rat and B6C3F1 mouse have not shown the same spectrum of carcinogenic activity as that found with phenolphthalein, suggesting that phenolphthalein estrogenic activity alone is not responsible for the spectrum of tumors observed. It is more likely that the multiple biological properties of phenolphthalein, including its ability to form free radicals, its clastogenic activity, and its estrogenic activity, contributed to the carcinogenic effects observed. These studies show that phenolphthalein is a multisite/multispecies carcinogen. One of the sites for neoplasm that is of particular concern is the ovary, and epidemiology studies are under way to identify any potential effects of phenolphthalein exposure at this site in humans.

Different mechanism of saturation of acetaminophen sulfate conjugation in mice and rats

Sulfation of acetaminophen is a high-affinity and low-capacity conjugation pathway in rats. It is thought that sulfation becomes saturated in rats at high doses of acetaminophen because of limited availability of the active sulfate donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), the supply of which is, in turn, limited by the availability of its precursor, inorganic sulfate. The present study was designed to determine whether a similar mechanism is responsible for capacity-limited sulfation in mice. Saturation of acetaminophen sulfation occurs in both species; however, at the maximal rate of sulfation, sulfate and PAPS concentrations were markedly decreased in rats but not in mice. Administration of sodium sulfate and the sulfate precursor N-acetylcysteine enhanced the formation of acetaminophen sulfate in rats, but not in mice. Mice exhibited lower activities of hepatic PAPS synthetic enzymes (i.e., ATP sulfurylase and APS kinase) and sulfotransferase than rats, which may in part be responsible for their lower capacity to sulfate acetaminophen. In addition, administration of acetaminophen further decreased phenolsulfotransferase activity in mice. In rats, administration of acetaminophen did not influence hepatic sulfotransferase activity. These observations suggest that while the capacity of rats to sulfate acetaminophen is limited by the availability of PAPS, in mice it is limited by sulfotransferase activity.

Evaluation of the potential carcinogenic activity of Senna and Cascara glycosides for the rat colon

Anthraquinone glycosides of Senna and Cascara were investigated for their ability to induce aberrant crypt foci (ACF) in the rat colon mucosa, which are considered putative preneoplastic lesions. Dietary exposure to high doses of these glycosides for 56 successive days did not cause the appearance of ACF or increase in incidence of ACF induced by 1,2-dimethyl-hydrazine (DMH). However, in rats treated with both DMH and the highest dose of glycosides, the average number of aberrant crypts per focus, considered a consistent predictor of tumor outcome, was higher than in rats given DMH alone. These findings suggest that Senna and Cascara glycoside might behave as weak promoters in rat colon carcinogenesis.

[Effects of processing on specific toxicity and pharmacodynamics of radix Kansui, radix Achyranthis bidentatae and semen Armeniacae amarum]

The comparative toxicological researches on crude and processed drugs show that the activating action of Radix Kansui, Radix Achyranthis Bidentatae and Semen Armeniacae Amarum on EBV-EA can be decreased by processing. Processing can also decrease stimulating activity on mouse skin, inhibit tumor-promoting activity in two stage skin tumor promoting test and lapactic effect by Radix Kansui. Meanwhile the pharmacological effects of these drugs can be retained or increased by processing.

Genotoxicity of aloeemodin in vitro and in vivo

The present in vitro and in vivo experiments were undertaken to clarify the genotoxic potential of the hydroxyanthrachinone aloeemodin which can be found in different plant derived products for therapy of constipation. The results demonstrate that aloeemodin is able to induce mutagenic effects in vitro. Positive results were obtained in the chromosomal aberration assay with CHO cells, as well as in the Salmonella reverse mutation assay (frameshift mutations in strains TA 1537, TA 1538 and TA 98). No mutagenic potential of aloeemodin, however, was observed in the gene mutation assay with mammalian cells in vitro (HPRT assay in V79 cells). Each assay was performed in the presence and absence of an extrinsic metabolic activation system (S9-mix). In in vivo studies (micronucleus assay in bone marrow cells of NMRI mice; chromosome aberration assay in bone marrow cells of Wistar rats; mouse spot text [DBA/2JxNMRI]) no indication of a mutagenic activity of aloeemodin was found. Information about a possible reaction of aloeemodin with DNA was derived from an in vivo UDS assay. Hepatocytes of aloeemodin-treated male Wistar rats did not show DNA damage via repair synthesis. All these data suggest that aloeemodin is able to interact with DNA under certain in vitro conditions. However, in vivo the results that were negative did not indicate a genotoxic potential. Therefore, it may be assumed that a genotoxic risk for man might be unlikely.

The mechanism of lactitol (NS-4) in inducing adrenomedullary proliferative lesion in rats

We used 13-week repeated oral administration of lactitol as part of a study to clarify the mechanism by which lactitol induces the proliferation of adrenomedullary chromaffin cells. There was a marked increase in urinary calcium (Ca) excretion even though the lactitol administration had no effect on the blood Ca level. A tendency for an increase in adrenal venous blood epinephrine (EPI) and norepinephrine (NE) concentrations was seen. Organ weight measurement of adrenal glands revealed a tendency for an increase in absolute weight and a significant increase in relative weight. Morphometric analysis of adrenomedullary chromaffin cells showed a tendency for an increased total cell volume and a decreased numerical density; but, there was no conspicuous change in the total cell number. Determinations of the anti-bromodeoxyuridine (BrdU) and antiproliferative cell nuclear antigen (PCNA) antibody-positive cell counts showed a tendency for an increased proliferation rate for adrenomedullary chromaffin cells. Electron microscopy showed a slight increase in the number of Golgi apparatuses in these cells. Because the marked increase in urinary Ca excretion was concomitant with morphological changes that suggested the hyperfunction of chromaffin cells in the adrenal medulla and a tendency for an increased cell proliferation rate, we assume that persistent hyperfunction of the adrenomedullary chromaffin cells, which was mediated by enhanced Ca absorption from the intestinal tract, may have induced proliferative lesion.

Sennosides and aloin do not promote dimethylhydrazine-induced colorectal tumors in mice

In a model of dimethylhydrazine-induced colorectal tumors in male mice aloin- or sennoside-enriched diets (0.03%) did not promote incidence and growth of adenomas and carcinomas after 20 weeks. Furthermore, in anthranoid-fed mice no significant changes in serum electrolytes as well as parameters of hepato- and nephrotoxicity were observed.

Two-year carcinogenicity study with sennosides in the rat: emphasis on gastro-intestinal alterations

A carcinogenicity study was conducted by administering a purified senna extract via the drinking water to Sprague-Dawley rats of each sex for 2 years. The daily doses received were 0, 5, 15 and 25 mg/kg. Histopathological examination was restricted to tissues from the gastro-intestinal tract, liver, kidneys, adrenals and from tissues with any observed abnormalities or masses. A laxative effect was observed in high-dose females, and in mid- and high-dose males. No significant differences in survival were found between treated and control groups. Mean body weight gain was significantly decreased in high-dose males. Increased kidney weights were noted in mid-dose males and females, and high-dose females. Histopathological examination of control and high-dose rats did not indicate any difference in the incidence of neoplastic lesions. As regards non-neoplastic lesions, a treatment- but not dose-related increase in reactive mesenteric lymph node hyperplasia was observed in preterminally sacrificed rats. However, a corresponding increase was not noted in the terminally sacrificed rats or when preterminal and terminal animals were combined. No ultrastructural changes in the myenteric nerve plexus of the colon and jejunum could be detected in the small number of investigated tissue samples. In conclusion, results from the present investigation do not indicate any relationship between long-term administration of purified senna extract and gastrointestinal, liver, kidney or adrenal tumors in the rat.

Chronic sennoside treatment does not cause habituation and secondary hyperaldosteronism in rats

Rats were treated with sennosides (6 x 10, 6 x 40 or 2 x 30 mg/kg weekly) or with danthron (6 x 500 mg/kg weekly) for 6 months. The laxative effect as measured by faecal wet weight during the first 10 h after treatment increased 3- to 4-fold by the higher sennoside doses (daily or intermittently) and 1- to 3-fold by danthron. The low sennoside dose had no measurable effect except on the 1st day (2 fold) compared with the control group. Mean faecal water content increased from 53% (controls) to 66-79% in rats treated with high sennoside doses and to 57 (1st day) -69% in danthron-treated rats. Serum aldosterone levels and mucosal Na(+)-K(+)-ATPase activities in the small intestine and colon did not change with treatment. There were no signs of habituation or secondary hyperaldosteronism due to sennosides or danthron in spite of chronic diarrhoea over 6 months.

Long-term mucosal alterations by sennosides and related compounds

Sennosides and related compounds are presumed to be severe cell poisons after prolonged ingestion. Some histological and ultrastructural studies in animals and man with such laxative misuse have revealed myenteric plexus and colonic epithelium injuries; but others have failed to point out identical data. In a first histological and ultrastructural study in mouse, we were unable to find any intestinal mucosa injury after long-term sennoside ingestion. In a second long-term experiment, we compared the effects of sennosides and 1,8-dihydroxyanthraquinone (synthetic anthracene derivative) on the mouse jejunum and colon. Electron microscopic observations showed nervous myenteric plexus abnormalities only in 1,8-dihydroxyanthraquinone-treated animals. These results suggest that sennosides have a good intestinal mucosa tolerance as opposed to aglycosidic-related compounds.

Toxic effects of sennosides in laboratory animals and in vitro

Sennosides were tested in a wide range of toxicity studies to evaluate risk assessment. From acute studies, sennosides could be classified as only slightly toxic in rats and mice after a single oral dose. The LD50 values were about 5,000 mg/kg in both species. The cause of death was probably due to an extensive loss of water and electrolytes following massive diarrhoea. In subacute studies with rats (max. 20 mg/kg) and dogs (max. 500 mg/kg), sennosides caused no specific local or systemic toxicity. Minor increase in kidney weight in rats was toxicologically not relevant. In a 6-month study with rats, sennosides were tolerated without specific toxic effects in doses up to 100 mg/kg. Effects on food consumption, body weight gain and some biochemical parameters as well as slight renal lesions can be interpreted as secondary effects following chronic diarrhoea. Mutagenicity tests and reproduction toxicity studies showed no abnormal results.

Electron microscopical studies on rat intestine after long-term treatment with sennosides

After gastric administration of daily 100 mg sennosides/kg body weight, no morphological differences could be found between the colon of treated rats and the controls. In particular, no damage to the intramural nerve tissue could be seen under the electron microscope.

Evaluation of the effects of sennosides on uterine motility in the pregnant ewe

The effects of sennosides on uterine motility were evaluated by electromyography in healthy adult ewes between day 70 and 120 of pregnancy to assess possible disturbances of the physiological pattern of contractility and eventual risks in pregnancy maintenance. At this stage of pregnancy, the ovine genital tract presented motility episodes of 6-8 min duration occurring at approximately hourly intervals. A dose-range study (10-160 mg/kg intracolonically) in 2 ewes showed that diarrhea was systematically obtained with doses greater than 20 mg/kg and was connected with a marked depression of both ileum and spiral colon motility. A standard dose of 60 mg/kg administered intracolonically 1-3 times at 7- to 10-day intervals to 12 ewes was used in the uterus studies. The experiments showed that sennosides did not stimulate uterine motility in the pregnant ewe, but slightly depressed it in some ewes. Cervix motility was never influenced. Intolerance of the drug was observed in half of the animals resulting mainly in anorexia or weakness and confirming a specific toxicity of senna in ruminants which is not known from other species. These effects were not related to uterine motility and pregnancy maintenance was normal in all ewes.

Laxative potency and acute toxicity of some anthraquinone derivatives, senna extracts and fractions of senna extracts

This paper investigates the laxative effect and acute toxicity of certain fractions of senna extracts in mice. The same tests were also carried out with several pure anthraquinone derivatives common in senna pods. The results show that the laxative and toxic components of senna pods and senna extracts can be separated. The most potent laxative components, sennosides A + B and Fraction V (relative potencies 1 and 0.9 respectively), have the lowest toxicity (relative intravenous toxicities 1 and less than 1). Fractions with very low laxative activity (rhein-8-glucoside and Fraction IV, relative potencies 0.56 and 0.05) have the highest acute toxicity (relative toxicities 10 and 32 respectively).